BM 100 A Reflex-Radar
BM 100 A Reflex-Radar
BM 100 A Reflex-Radar
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Level measurement: Level pulse amplitude and threshold<br />
After connection to a power supply, the <strong>BM</strong><strong>100</strong> A will:<br />
1. Measure reflection pulses in terms of voltage amplitude by cycling through a set of gains.<br />
2. Identify the highest amplitude as being the product level.<br />
The diagram below shows a level threshold of 2.71 Volts for a Gain of 1.<br />
1 Initial pulse<br />
2 Flange reflection (except<br />
coaxial probe)<br />
3 Non-product reflection<br />
(e.g. parasite : agitator)<br />
4 Product level reflection<br />
5 Level threshold (with 2<br />
metre steps). Set in user<br />
function 1.5.1.<br />
6 Offset (see below for<br />
definition)<br />
7 Distance measured as a<br />
function of time<br />
Offset is the distance measured as time for the signal to travel from the signal converter to the<br />
flange (the gauge’s reference point).<br />
If difficulties are experienced finding the correct level, try the following solutions.<br />
• User function 1.1.4 Window Frozen set to “Yes”:<br />
Critical Parameter: Ask KROHNE for more advice before reconfiguring gauge.<br />
This concentrates search for product level in a small defined zone and ignores interference<br />
signals.The gauge will set up the “level window” on either side of the last reading with a plus/minus<br />
range equal to half of the value given in Function 1.1.5. The gauge will then ignore all other pulse<br />
reflections outside the “level window” as long as there is a reflection above the pre-set threshold. If<br />
no pulse is detected, the instrument will change the Gain automatically as the pulse changes<br />
amplitude.<br />
• User function 1.1.4 Window Frozen set to “No”:<br />
The instrument will search along the entire length of the probe. Warning : This may lead the<br />
instrument to incorrectly identify a non-product reflection (e.g. a nearby beam or the nozzle) to be<br />
the current level.<br />
• Modification of User Function 1.5.1 Level Threshold:<br />
Critical Parameter: Ask KROHNE for more advice before reconfiguring gauge.<br />
The default threshold values do not normally need to be changed. However, the level threshold may<br />
need to be modified if level is hard to detect due to parasite signals from obstructions in the tank<br />
(nozzle, beams and mixers) or the measurement of products with very low dielectric constants.<br />
42 Handbook <strong>BM</strong> <strong>100</strong> A