Precision Hygrothermometer TH309 With USB ... - Temperatur-Shop

Precision Hygrothermometer TH309 

With USB-Interface 

Operating Instructions 

0560 0309 

B+B Thermo-Technik GmbH 

Heinrich-Hertz-Straße 4 

78166 Donaueschingen 

Tel. +49 771 83160 

Fax +49 771 831650 

E-Mail: info@bubthermo.de

TH309, Stand: 01.09.2006 

B+B Thermo-Technik GmbH, 78166 Donaueschingen, Heinrich-Hertz-Straße 4, Tel. +49 771 83160, Fax +49 771 831650 

www.bubthermo.com, www.bubthermo.de, E-Mail: info@bubthermo.de 

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Table of Contents 

1................ FOREWORD .............................................................................................................................................. 4 

2................ GENERAL INFORMATIONS ...................................................................................................................... 5 

2.1. ............ Labels ........................................................................................................................................................ 5 

3................ Security advices ....................................................................................................................................... 6 

4................ WASTE AND DISPOSAL ADVICES ........................................................................................................... 6 

5................ Usage according to purpose .................................................................................................................... 6 

6................ PRODUCT DESCRIPTION ......................................................................................................................... 7 

6.1. ............ Interfaces ................................................................................................................................................... 7 

6.2. ............ Power Supply ............................................................................................................................................. 8 

7................ STARTUP AND OPERATING ELEMENTS ................................................................................................. 9 

7.1. ............ Ansicht des Gerätes.................................................................................................................................... 9 

7.2. ............ Electrical Connections................................................................................................................................. 9 

7.3. ............ Power Supply adaptor............................................................................................................................... 10 

7.4. ............ USB-Interface........................................................................................................................................... 10 

7.5. ............ Display ..................................................................................................................................................... 10 

7.6. ............ Function keys ........................................................................................................................................... 11 

7.7. ............ Startup ..................................................................................................................................................... 11 

7.7.1. .......... Several devices on one PC ....................................................................................................................... 11 

7.8. ............ Auto power off and activation of the USB interface..................................................................................... 12 

7.9. ............ Displaying of the dew point and absolute humidity ..................................................................................... 12 

7.10............ Displaying the Minimal- and Maximal values.............................................................................................. 13 

7.11............ Chnaging the temperature unit .................................................................................................................. 14 

7.12............ HOLD-Function......................................................................................................................................... 14 

8................ Calibration and adjusting ....................................................................................................................... 15 

8.1. ............ Important advices ..................................................................................................................................... 15 

8.2. ............ General advices for calibration .................................................................................................................. 16 

8.3. ............ Premises for the calibration....................................................................................................................... 16 

8.4. ............ Proceeding a recalibration......................................................................................................................... 16 

8.4.1. .......... Key functions in the calibration mode......................................................................................................... 16 

8.4.2. .......... Preparing the calibration of temperature .................................................................................................... 17 

8.4.3. .......... Proceeding the temperature calibration...................................................................................................... 17 

8.4.4. .......... Preparing the humidity calibration.............................................................................................................. 19 

8.4.5. .......... Proceeding the humidity calibration ........................................................................................................... 20 

9................ Error warnings ........................................................................................................................................ 23 

10. ............. USB-Interface protocol ........................................................................................................................... 23 

10.1............ Configuration data line .............................................................................................................................. 24 

10.2............ Structure of the measured value data line.................................................................................................. 24 

11. ............. Maintenance............................................................................................................................................ 25 

12. ............. Questions................................................................................................................................................ 25 

13. ............. Technical data......................................................................................................................................... 26 

14. ............. Bestellangaben .........................................................................................Fehler! Textmarke nicht definiert. 




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1. FOREWORD 

Dear customer, 

We thank you for having purchased the Precision Hygrothermometer TH309 and are very glad 

that you decided in favour of a product of B+B thermo-Technik GmbH. We hope this product will 

fully satisfy you and will assist you effectively in your work. 

This Device has been developed to be technically highly up-to date. This product has been 

designed in accordance with the regnant European and German national directives and rules. For 

a proper and effective usage of the product the customer shall observe the following Operating 

Instructions. In the case that against one’s expectations any troubles occur which you can not 

resolve yourself, please contact our service centres or your salesperson. We go after giving you 

rapid and competent help to minimize the risk of long time outfalls. 

The following operating Instruction is an indispensable part of this Product. It contains important 

advices for the starting up and further use of the device. 




4 / 26

2. GENERAL INFORMATIONS 

This documentation contains information which must be paid in attention to assure a highly 

effective and secure use of the supplied product 

Please read through the following instructions and make yourself familiar with the handling of the 

product before you insert it in your processes. Keep this document always readily to hand so you 

can consult it by need. 

2.1. Labels 

Sign Meaning Notice 

It is necessary to read the following advices before 

beginning the operations. The used symbols in the 

Advice 

manual acts first of all as eye catcher for security 

risks. The symbols do not replace the security 

advices. The text must be read to the end. 

This symbol designates important advices and tips 

Necessary to observe that are necessary for the success a work step. They 

have to be followed in order to get good results. 

Warning 

Signs 


Meaning 

This symbol advises the user of 

danger for persons, material or 

environment. The text gives 

information that must be 

necessarily followed to avoid 

any risks 

Caution against hot surfaces 

(BGV A8, GUV-V A8/W26) and 

hot liquids or substances 

Caution against liquids and hot 

substances 

Caution against dangerous 

explosive substances (BGV A8, 

GUV-V A8/W02) 

Caution against mobile engines 

(W29) 

Caution against moving parts 

Warning 

Signs 

Meaning 

Caution against electromagnetic 

fields (BGV A8, GUV-V A8/W12) 

Caution against severe cold 

(BGV A8, GUV-V A8/W17) 

Caution against dangerous high 

electrical voltage (BGV A8, 

GUV-V A8/W08) 

Caution against dangerous 

explosive atmosphere 

(BGV A8, GUV-V A8/W21) 

Electronic waste 



5 / 26

3. Security advices 

B+B Thermo-Technik GmbH assume no liability for damages occurred through failure to observe 

these security advices. A usage non conform to the instructions given in this manual can damage 

the device 

A usage non conform to the instructions given in this operating manual can cause reversible or 

irreversible damages to the device and can harm the operator. 

Body and property damages 

• The use of the measurement system must be restricted to qualified personal 

• The sensor input socket / Plug shall never be put under Voltage. 

• In industrial establishment the accident prevention instructions must correspond to the local 

government safety organisation and to the local corresponding employer's Liability Insurance 

Associations rules. 

• The system may not be used in atmospheres with explosion danger. 

• The system is not adequate for the use on animals or living creatures. 

• Keep the system away from Childs. 

• Do not stock the product together with solvents. 

• Do not use the system on mobile parts. 

• Do not expose the system to high vibrations, collisions or pressure. 

• Do not expose the system to high electromagnetic fields. 

• Do not use the system in medical applications. 

Ensuring of the product security 

• The system must be operated only within the limits given in the technical Data 

• Do not open or try to open the system. 

• The calibration of the system must be controlled from time to time. If needed the system 

must be recalibrated. 

• The user has to periodically control, whether a new recalibration is needed. The user has to 

supervise the recalibrations. 

• Keep the system always clean. 

4. WASTE AND DISPOSAL ADVICES 

Please return the device to B+B Thermo-Technik GmbH after expiration of its lifetime. 

5. Usage according to purpose 

Please use the product only for the purposes for which it is conceived. In case of doubt, please 

first contact B+B Thermo-Technik GmbH. 

The compact measuring system is adequate for precision temperature and Humidity 

measurements. 




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The system may be used in all applications that are not in contradiction with the notes in the 

security advices. 

The following application domains are explicitly excluded: 

• Zones with explosion danger / risk 

• Diagnostic measurement in medical domains 

6. PRODUCT DESCRIPTION 

The hand held measuring instrument TH309 is a highly precise hygrothermometer, conceived for 

a wide variety of applications. It can be used for example in climatic measurement purposes, in 

the home controllingindustry or in quality controlling applications. It can be also used in more 

special applications such as in the compressed air measurement techniques. A variety of 

adequate probes, which cover almost all types of applications, are available. Special customized 

probes can be deliverd on request. The high precision and the long term stability of the used Thin 

film ceramic sensors has to be especially pointed out. This guarantees a minmum of necessary 

new re-calibrations. 

The mesurment results of temperature and Humidity are simultaneously displayed on the concise 

LCD display of the device. A special feature of the TH309 instrument is the ability to compute the 

pressure dew point and absolute humidity. The computed quantities can be visualized with a 

simple keystroke. The minimal and maximal measured values can be also displayed with a 

keystroke. 

The precision and accuracy of the measured humidity values can be user-controlled by using 

Humidity referece cells, which can be purchased as accessory from B+B Thermo-Technik GmbH. 

With the aid of these reference cells at every time readjusted thank the integrated Calibration 

function. 

The USB interface is used to connect the measuring device to a PC system or laptop. The B+B 

thermo-View software, which can be optionally purchased, provides a powerful tool to 

automaticallly collecti and protocoll of measuring data. This makes the device very useful also as 

stationary measuring instrument The software permits also the graphical visualization of the 

relative humidity and temperature as well as many other (computed) physical quantities. 

The measurement of relative humidity and temperature is effected through an external hand held 

probe, which can be easily exchanged whithout need of readjustement of the device. As 

accessories a variety of hand held probes, matching the requirements of different application 

types, are available. 

6.1. Interfaces 

USB-Interface 

The communication between the Measuring instrument and the PC system is effected through 

the USB interface. The total USB cable length may not exceed 5 m. The use of low quality 

extension cables can results in an interference and noise sensitivityalong the USB cable. This 

can grow up to a disconnection of the interface. Adequate extension cables are available by B+B 

Thermo-Technik. 




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6.2. Power Supply 

The TH309 device is power supplied through a standard 9V-Block battery or through the USB 

interface if used. Optionally it can be operated with a power line adaptor, which is included in 

package. 




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7. STARTUP AND OPERATING ELEMENTS 

7.1. Ansicht des Gerätes 

7.2. Electrical Connections 


HYGROMETER 

MI 

N 

B+B 

%R 

LCD Display 

Keypad with 6 

function buttons 

The Hygrothermometer has three different sockets on its upper side. 

External power supply (Adaptor) 

Connection fort he probe 

Serial USB interface socket 



°C 

ON Hold °C/°F 

td/aH MIN/ 

MAX 

RST 

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7.3. Power Supply adaptor 

In the case of using the hygrothermometer as stationary measuring device, The instrument must 

be powered with a constant 12V. In this case the battery is automatically disconnected. 

Please use only a high quality and stabilized power line adaptor. The power supply voltage may 

not exceed 12 V. The central pin of the plug must have the positive voltage. 

Please avoid any electrostatic discharges on or near the electric connections of the instrument. 

This can cause irreparable damages to the device. 

7.4. USB-Interface 

The Hygrothermometer TH309 offer eine potential free serial data interface, which permits the 

direct connection of the device to a PC system orr laptop, where the collected data can be 

processed and saved. The transmission is effected as ASCII-code with 4800 Baud, 8 databits, 

no parity and 1 stop bit. For more information on the data format please refer to the end of this 

document. 

7.5. Display 

The 2- lines concise LC-Display is used in the normal mode to display the actual measured 

values of temperature and humidity. 

Function im normal operating mode Display 


Relative humidity in %RH 

Temperature in °C 

B+B Thermo-Technik 



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7.6. Function keys 

Bezeichnung Funktion 

ON 

HOL 

D 

°C/°F 

td/a 

H 

MIN/ 

MAX 

RST 

7.7. Startup 


ON / OFF button 

Hold function. The actual measured values are hold on the display. This permits the easy 

reading of values in fast processes. 

This key permits the switching between the temperature units °C and °F 

Switches the displaying of humidity values to dew point (td) or absolute humidity (a) 

Min and Max values will be diplayed 

Reset of the Min and Max values. 

The device is delivered ready for operation and calibrated. To operate the system for the first 

time, the user must open the battery case on the rear panel of the instrument and insert the 

batterie. Please pbserve the polarity of the connections. Close the the battery case again. 

The probe may be connected only whith the device powerd off. Turn off the instrument first if you 

want to connect or change the probe. The probe or the instrument can be irreparably damaged if 

the sensor is connected while the device is On. 

Avoid electrostatic discharges on or near the device’s connectors. Electrostatic discharges can 

destroy irreparably the probe, the measuring instrument or both. Together. 

Turn off the TH309 device. Connect the plug of the probe to the socket on the upside of the 

instrument. The arrow on the plug must show downwards. 

Press the ON/OFF button to power on the instrument. The actual measured temperature and 

relative humidity are shown then on the display. 

7.7.1. Several devices on one PC 

The user can operate several instruments on one and the same PC system. If the PC has only 

one USB socket the user must provide a USB splitter or terminal block to be able to connect 

several instruments to the PC. 



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7.8. Auto power off and activation of the USB interface 

The device is equiped with an auto power off tool. To save the batterythe instrument switches off 

itself automatically after 10 minutes user inactivity. The user has the possibility to deactivate this 

feature in order to be able to make long time measurements for example or when usig the power 

line adaptor. The USB interface is activated only when the auto power off feature is deactivated. 

Button Operation Response Display 

ON 


When powering up the 

instrument please hold the 

ON /OFF key pressed until 

LOG is displayed on the 

screen 

Auto power off is deaktivated. 

USB-interface is active 

Actual measurement values are 

displayed 

When the instrument is switched off and then On (ON/OFF key once pressed) the auto 

power off feature is reactivated 

7.9. Displaying of the dew point and absolute humidity 

Instead of the “normal” temperature the user can set the instrument to display either the dew 

point temperature or the absolute humidity. 

Bedienung der Tasten Rückmeldung Display Anzeige 

Td / aH 

Td / aH 

Press once the [td/aH] 

button 

Device is in “normal” mode 

Press the [td/aH] button a 

second time 

Instrument switches to dew point 

displaying 

„td“ appears on the display 

Displaying of the absolute humidity 

Values are in units of g/m 3 







12 / 26

td/aH 


A new press of the 

[td/aH]- key 

“Normal” operation mode 

7.10. Displaying the Minimal- and Maximal values 

Instrument displays Temperature and 

relative humidity 

The instrument determines automatically the lowest and highest measured values since the last 

power ON or the last resetting (RST-Key). These values can be displayed on need. 


td/aH 

Min/M 

ax 

Min / 

Max 

td/aH 

The instrument is in the “normal” operation mode 

Min/ 

Max 

Press the MIN/MAX-key 

Press the MIN/MAX-key a 

second time 

The Min. Values is 

displayed on the screen 

„MIN“ appears on the 

dispaly 

The Max. Values is 

displayed on the screen 

„MAX“ appears on the 

dispaly 

When the device is on the dew point or absolute 

humidity displaying mode, the displayed MIN/MAX- 

Values corresponds to the displayed quantity 

To go back to the normal mode, press td/aH-Taste and 

MIN/MAX- Key several times till the instrument displays 

again the RH and temperature values 








%R 

MIN °C 


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RST 


RST-key can be pressed 

every time 

7.11. Chnaging the temperature unit 

Resets the Min / Max values 

The measured temperatures can be displayed either in °C ( Celsius) or in °F (Farenheit). 


°C/°F 

°C/°F 

Instrument is in normal operating mode 

Press the °C / °F-key 

Press the °C / °F-key 

Temperature values switche to °F units 

„°F“ appears on the display 

Temperature values switche to °C units 

„°C“ appears on the display 

The selected temperature unit is valid for all temperature quantities (dew point, Min, Max..). The 

data transmission format to the USB is not affected through this selection. It is always in °C. 

7.12. HOLD-Function 

B+B Thermo- 

B+B Thermo- 

To make the reading in fast processes easier, the TH309 offers the possibility to hold the 

measured value on the display. This HOLD-feature falicitates also the reading in bad illumination 

circumstances. 




14 / 26

HOLD 

td/aH 

MIN/ 

MAX 

HOLD 


Press the HOLD-key 

Device is in Normal Mode 

Actual measured value is hold on 

the screen 

„HOLD“ appears on the display 

The HOLD feature is valid also for all disolayed quantities 

Pressing the HOLD-key again 

8. Calibration and adjusting 

8.1. Important advices 

Instrument returns to the normal 

mode 





The humidity sensors are calibrated before delivery in a laborious and time-consuming complex 

process. Adjustment of new delivered sensors is useless because a better accuracy can not be 

reached. 

The precision probes, some special probes and the dew point probes are calibrated ex works at 

at several temperature and humidity points. This probes can not be calibrated with the TH309 

device and must therefore sent to our works if new recalibration is needed. Thogh a control of 

the measuring accurcy is possible with the use of the rference cells. 

Probes that have been calibrated within an ISO- or DKD-Calibration process (delivered with 

Calibration certificate), may be only controlled but not adjusted from the user himself. Otherwise 

the calibration certificate looses its validity! 

Reference cells are classified as Standards of the humidity. The cells must be regularly controlled 

with a certified Reference measurement device. The result of a new adjustement must be 

controlled in a comparative measurement with a certified rference measurement device. 



15 / 26

The hunmidity probes are protected against unwanted adjustement and / or overwriting the 

calibration data. To proceed a new calibration the overwrite protection must be first deactivated. 

Further information are in the documentation of the probe. 

8.2. General advices for calibration 

The temperature measuring part of the device has in general a very good longtime stability. A 

new recalibration or adjustement is therefore necessary only if the sensor has been changed or 

the calibration data has been unwillingly destroyed. In case the measured temperature values are 

all right please skip the temperature calibration part. 

To readjust the humidity the temperature measuremnt must be correct, otherwise the internal 

temperature compensation will not be valid and the measured humidity looses in accuracy. 

Please control the state of the sensors and make sure the device is working correctly before 

every calibration / adjustement process. Defect or mechanically damaged sensors must be 

exchanged before the calibration. Defect measuring devices must be repaired. 

8.3. Premises for the calibration 

The calibration of the temperature part is effected at 23 °C and 60 °C. The Reference 

temperatures must be set with a precise air circulation cabinet. In addition a DKD calibrated 

precise measuring reference cell is required. 

The calibration of the humidity measuring part is effected at the points 75 %RH and 33 %RH. The 

reference humidity values have to be set with rference cells. The state of these cells has to 

carfully controlled (operating instructions of the reference cells). The humidity adjustment must be 

effected in an absolutely temperature stable environment. We recommend to processd the 

adjustement in an air-conditionned labor at 23 °C ±3 K and 50 %RH ±5 % RH. 

The user must have profound physical knowledges in the domains of thermodynamic. 

Any calibration process may not be proceeded when the equipment is incomplete and/or by 

deficiencies in the technical knowledges because once such a process is started the actual 

calibration data are lost. Please send the device to our calibration labor in this case. 

8.4. Proceeding a recalibration 

8.4.1. Key functions in the calibration mode 

The keys have fully other functions in the calibration mode than in the normal mode. Please read 

through first this part of the documentation and set the deliverd pattern on the front panel of the 

device. 

Taste Bezeichnung derTaste Funktion im Kalibriermodus 

ON 


ON-key Start / End of the calibration mode 



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TEMP/ 

RH 

POINT 

Store 

UP 

DOWN 


TEMP/RH-key Toswitch between the temperature and humidity calibration parts 

POINT-key Switching between the different calibration points 

STORE-Taste To save the calibration / adjustment value 

UP-key To increase the adjustment value 

DOWN-key Todecrease the adjustment value 

8.4.2. Preparing the calibration of temperature 

Required are: 

• A calibrated Thermometer with high accuracy 

• A precise and highly constant air-circulation cabinet with setting range 23...60°C 

If the measued temperature values are correct please skip this part of the calibration process. 

If aan adjustment of the temperature measurment is needed, please proceed as follow: 

The calibration of the temperature can be proceeded with the protection filter set. Place the 

reference probe in direct neighborhood of the probe to be calibrated in the air circulation cabinet. 

Set the temperature of the cabinets to 23,0°C. Wait until the temperature is stable. 

The stability of the temperature reference point determines the accuracy of the calibration. The 

used reference measuring device must be at least a class better (accuracy) than the device to be 

calibrated. 

Advice: air-circulation cabinets are in general not enough stable and have often local 

inhomogeneities in the temperature distribution. Different time-constants take place between the 

refernce and the controlled probes. 

The reference probe and device can be used to control of the stability of the cabinet: The 

displayed value must be stable up to the first decimal position. 

8.4.3. Proceeding the temperature calibration 

Key operation Response Display 

Prepare the calibration at 23°C as described above. Proceed further first when both temperatures are stable 



17 / 26

ON 

ON 

TEMP/ 

RH 


Simultaneously press the 

ON- and TEMP/RH-keys 

- and hold both pressed 

until is displayed 

First switch off the instrument 

The instrument switches to the 

calibration mode. The lower display 

line shows the lower calibration point 

( ) at 23°C. 

Read out the real temperature value on the reference instrument and set it in the TH309 device as follow: 

UP 

DOWN 

Store 

Use the UP- or. DOWN-key 

to set the value read in the 

rference instrument. 

Confirm the value set by 

pressing the STORE-key 

The calibration point is set to the 

measured value in the reference 

measuerment instrument. 

TH309 Instrument is set to the given 

temperature. 

blinks in the lower display line 

and the value set is displayed again. 

The calibration of the lower point is fullfilled. To continue the calibration process, the air 

circulation cabinet (thermostat) must be set and stabilised to the upper calibration point (60°C). 


POINT 

Hold the POINT-key 

pressed untill is 

displayed 

The lower line in the display shows 

the upper calibration point ( )at 

60,0°C 







18 / 26

UP 

DOWN 

Store 


Use the UP- or. DOWN-key 

to set the value read in the 

reference instrument 



The calibration point is set to the 

measured value in the reference 

measuerment instrument 

TH309 Instrument is set to the given 

temperature. 

blinks in the lower display line 

and the value set is displayed again 

The calibration process of the temperature measuring part in the TH309 is complete. The process can be finshed 

by pressing the ON-key. 

8.4.4. Preparing the humidity calibration 



For the calibration following tools are required: 

• A set of reference cells (33%RH and 75%RH) 

• Eventually a clampinring adapter to the cells. (not needed for the probes of type D) 

• A styrofoam box 

• The operating instructions of the reference cells 

Unscrew the protection filter and remove it axially and carefully from the probe. The 

sensors are then unprotected and very susceptible to to damages. 

Control the state of the sensor element. Damaged or scratched elements must be exchanged. 

Soiled sensors must be cleaned in distilled water, then dryed by 80°C for at least 24 hours in a 

thermostat and finally stocked by 50%RH for at least 48 hours. 

Carefully mount the clamping fixture on thze probe. The teflon gasket ring lies on the stainless 

steel housing. 

The instruction and the security advices of the reference cells must be strictly observed. Unscrew 

the cap from both reference cells and control their interior chamber. Entered liquids must be 

carefully removed using a fusselfree cloth. Control the fill level and the saturation of the 

saltsolution in the cells. Damaged or defect cells mus be rejected! Close the MgCl-cell 

immediately after the control. You will need it first for the adjustment of the second calibration 

point. 

Screw in the probe with the clamping adaptor on the NaCl-cell. Avoid any contact with the palm of 

hands to exclude any thermal inhomogeneities. Place the the probe and the cell in the styrofoam 

box. The measuring instrument TH309 must stay outer the box. Close the styrofoam box and wait 



19 / 26

for at least two (2) hours. Switch on the TH309 instrument from time to time to control the stability 

of the the temperature. The temperature fluctuation may not exceed 0,1°C. 

After two hours and when the temperature is stable, the user can go on with the calibration 

process. Please note down the actual temperature value measured with instrument. 

8.4.5. Proceeding the humidity calibration 



Prepare the calibration as described above and control the the temperature stability on the 

TH309 device. Go on with calibration first when the temperature is stable. 

ON 

ON 

TEMP/ 

RH 

TEMP/ 

RH 

Hold the ON- and 

TEMP/RH-key 

simultaneously pressed 

untill appears on the 

display 

Press the TEMP/RH-key 

untill is displayed 

First, Switch off the instrument 

Instrument switches to the calibration 

mode. 

The lower line in the display shows 

the lower temperature calibration 

point at 23°C 

Device switches to the humidity 

calibration part. 

Upper line in the display shows the 

upper calibration point ( ) ati 75.0 

%RH 

The actual relative humidity reigning in the reference cell must be determined with aid of the table of values 

delivered with the reference cell that correspond to the temperature value in the styrofoam box. The hmidity value 

must interpoled if necessary. 

UP 

DOWN 

Use the UP-and. DOWNkeys 

to set the determined 

relative humidity value 

Calibration point is set the relative 

humidity value of the reference cell 

Upper display line shows the value 

set 






20 / 26

Store 




Instrument is set to the given humidity 

value. 

The value is saved, blinks in 

upper display line 

Afterthere the value set ishowed on 

the display. 


The adjustement of the upper calibration point is realised. Now the lower (second) humidity calibration point ( ) 

must be adjusted. 



21 / 26


Change carefully the reference cell as done for the the first one. Wait again 2 hours and for the 

temperature stabilisation. Note down the measured temperature. 

POINT 


Press the POINT-key untill 

is displayed 

Upper line in the display shows the 

upper calibration point ( ) ati 33.0 

%RH 

The actual relative humidity reigning in the reference cell must be determined with aid of the table of values 

delivered with the reference cell that correspond to the temperature value in the styrofoam box. The hmidity value 

must interpoled if necessary. 

UP 

DOWN 

Store 

Use the UP-and. DOWNkeys 

to set the determined 

relative humidity value 



Calibration point is set the relative 

humidity value of the reference cell 

Upper display line shows the value set 

Instrument is set to the given humidity 

value. 

The value is saved, blinks in 

upper display line 

Afterthere the value set ishowed on 

the display. 




The calibration of the humidity part is achieved. Leave the calibration mode by switching off the instrument 



22 / 26

9. Error warnings 

Blinking display, accustic signal or “Err”: are advices for low battery. After the first occurrence of 

this error message the user can measure without error for about one hour. Please exchange the 

battery or use the power line adaptor. 

Important advice: Please use only leakage free Alkali-Mangan batteries, otherwise the device can 

be damaged. Please remove the battery when the instrument is not used for a long time. 

„- - -“ indicates that no probe is connected to the instrument or the sensor is uncalibrated. Please 

make sure the probe is connected the right way to the device. 

„Err“ : is an error message that advices the user to one of the following probable errors: 

• Humidity and / or temperature sensor is defect 

• Adjustment data saved in the eeprom are not plausible 

If the sensors are not defect and the probe is connected the right way then therror can be in 

general corrected by a new recalibration. Otherwise please send the instrument to our customer 

service. 

10. USB-Interface protocol 

The interface setting must be as follow: 

Baud: 4800 Baud, 

Data bits 8, 

Parity None 

Stopbit 1 

The data transmission occures in lines of ASCII codes. The informations are continuously 

transmitted without spacing character. Every line contains the information data of only one 

chanel. The two last characters of every line represent the control code (CRC) for the line. Every 

line ends with (carriage return) character. Several lines buil a data block. A datablock can 

have for example the following contains : 

@ 

I01010100B00725030178 

V010892A1 

I02020100B00725030148 

V0216B0EA 

$ 

The Data blocks have always the following structure: 

• @: Synchronisation code that signals the begin of a data 

• The configuration data (Identifier) of a channel. The data line begins with ‘I’, followed by the 

logical channel number, then the configuration data and then the sensor serial number. The 

line is concluded with the CRC and . 




23 / 26

• The measured values of a channel. The data line begins with the character ‘V’ (for Value), 

followed by the logical channel number, then the measurement value. The line is concluded 

with the CRC and . 

• Every data block is concluded with the synchronisation code ´$´ ´. 

10.1. Configuration data line 

The configuration data line contains all information available about the sensor used in the 

corresponding channel. The structure of the line is as follow: 

• ‘I’ character for “Identifier” I01010100B00725030178 

• 8 Bit (two ASCII-characters) logical channel number. This number is used to assign the 

configuration data to measured data. When using temperature and humidity probes, the 

channel 01 is assigned to the temperature and 02 to the humidity. 

I01010100B00725030178 : temperature 

• 8 Bit (two ASCII-characters) physical probe identification. With the probe identification are 

transmitted: the number format, the scaling, the physical unit, and the admissible value 

range. 

I01010100B00725030178: standard 

• 8 Bit (two ASCII-characters) Identification of the probe type. Temperature / humidity probes 

have the 01 as identifier. 

I01010100B00725030178: Temperature Humidity probe 

• 48 bit (twelve ASCII-characters) Sensor serial number. 

I01010100B00725030178: Serial number 

• 8 Bit (two ASCII-characters) CRC. 

• ´´line ending 

10.2. Structure of the measured value data line 

• ´V´ to signal here begins a data line with measurement values. 

• 8 Bit (two ASCII-characters) logical channel number (01 for Temperature, 02 for humidity). 

V010892A1: temperature 

• 2 Byte (four ASCII-characters) measurment value. For temperatures with 0,01°C resolution, 

the hexadecimal value has to be changed in decimal value and divided by 100. The value 

obtained is the temperature in °C with two decimal positions. For the humidity with 0,005 % 

resolution the hexadecimal value has to be chaged in decimal and the divided by 200. The 

value obtained is the relative humidity in %RH with two decimal positions. 

V010892A1: 0x892 coresponds to 2194(decimal) divided by 

100 gives T = 21,94°C 

• 8 Bit (two ASCII-characters) CRC. 

• ´´ as line ending 

In the example showed above: the temperature has a value of 21,94° C and the relative humidity 

29,04% rF. 




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11. Maintenance 

Clean the housing with a wet cloth if necessary. Do not use hard detergents or solvents. With the 

exception of regular recalibration (or calibration controls) there are no further maintenance 

needs. The user has to control and determine when a new calibration is necessary. 

12. Questions 

For more informations please contact: 


Heinrich-Hertz-Straße 4 

78166 Donaueschingen 

Tel.: +49 771 83160 

Fax: +49 771 831650 

E-Mail: info@bubthermo.de 

www.bubthermo.de 

Your partner for temperature measuring 





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13. Technical data 

TH309 Hygrothermometer 

Powerful measuring device for temperature and humidity, absolute humidity, dew point and 

pressure dew point computation. High precise temperature compensated humidity measurement 

up to 1%RH accuracy. 2-line display for simultaneous displaying of temperature and humidity. 

Temperature in °C or °F, Min / Max values memory. HOLD feature. Auto power off. USB 

interface. 

features 

Measuring rate 2 Hz 

Special functions Computation of : Absolute humidity, dew point and 

pressure dew point, Min / Max memorisation, 

battery monitoring, auto power off 

Operating temperature (device) 0°C bis 50°C 

Interface USB 

Display 2-lines LCD, 37 mm x 42 mm 

Battery 9V, Alkaline IEC 6252 

about. 12 hours continuous operation 

Dimensions (LxBxT) 181 x 71 x 38 mm 

Humidity measurement, depends on the used probe, data are valid for 1308 STD 

Measurement range 0...100% RH 

Resolution 0,1% RH 

Resolution on the USB 0,01%RH 

Typical accuracy ±2 % RH 

Response time 10 Sec 

Temperature measurment, depends on the used probe, data for 1308 STD 

Measurment range –40...80 °C 

resolution 0,1 °C 

Resolution on the USB 0,01°C 

Accuracy ±0,5 °K 

Response time 10 Sec 

Housing ABS, black 

Delivered with Battery, Operating instructions 

accessories Special probes, pressure dew point probes, Case, 

Calibration set, USB Cable, Software, Power line 

adaptor 




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Precision Hygrothermometer TH309 With USB ... - Temperatur-Shop

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