Thermo Ramsey - Hoferick Engineering GmbH

Operation
1-6
1.7.1.3 Zero and Span Automatic Calibrations
Zero and span calibrations are based on belt length defined by a number of belt
revolutions.
To calculate the exact number of revolutions, the instrument counts the pulses
delivered by the speed transmitter (one pulse represents a specific belt length).
When the required number of pulses is reached, the instrument ends the
calibration test, and compares the actual totalized value to the theoretical one (0
for zero calibration), and calculates the calibration constant.
• Electronic Calibration (R-Cal) – Allows the user to perform the calibration
without the need for applying test weights or test chains on the weighbridge,
is performed by unbalancing the load cell bridge using a precision resistor.
The calibration constant is calculated based on the load cell and the scale
data.
• Test Weight Calibration – Requires the positioning of test weights on the
weighbridge.
• Chain Calibration – Requires the application of calibrated chains on the
belt. This method is the nearest to actual operating conditions.
• Material Test – Is performed by running a known quantity of material on the
scale and weighing that quantity on a static scale of known accuracy.
1.7.1.4 Zero Tracking (AZT)
Under a preset minimum flow rate when enabled, the instrument makes
subsequent automatic zero calibrations with the following sequence:
1. Waits for one-half time of the test duration (a solid “Z” displays);
2. Execution of a zero test (the “Z” flashes);
3. Performs automatic zero for one test duration;
4. Continuously repeats above zero calibration as long as feed rate remains
below AZT preset value.
Zero Tracking function is limited to a maximum value of “ZERO LIMIT” that is
set as a percentage in the SETUP scroll.
If the new zero calculated, by auto-zero tracking function, exceeds that value, an
alarm is generated, and the new zero is not installed. The reference value for
zero is set every time an Auto Zero or Manual Zero is performed.
Installation Thermo Fisher Scientific
REC 4175 Rev B