I am trying to understand the Optomux ‘Reading Negative Numbers and Temperature’ section on page 153 of the manual. My scenario is that I have no temperature modules but I do have some analog I/O modules I can use to generate the module input counts to verify my conversions for the various temperature probe types. I have implemented the piecewise linearisation calculations and as far as I can tell they generate the correct temperature values if I hand enter the counts. I would guess that if I leave the probe type set to 0 I can simulate the temperatures OK using a standard module.
What I am seeing is that setting a temperature probe type changes the value returned by ‘Read Analog Inputs’. The manual quote below did not say that I would have to set the probe type to 0 to keep the module counts from being altered by the B3000 in response to the probe type. I would not have expected setting a probe type to have altered the ‘Read Analog Inputs’ value.
It is plain that the B3000 does some computations when a probe type is set which makes it difficult to figure out what value to send to an analog input to generate a specific output value.
The manual says, ‘If temperature is outside the module’s nominal range (or if your software does not support the Read Temperature commands), then you will need to read counts from the module, linearize the counts, and convert them to temperature.’
Any tips on using a standard analog input module to simulate temperature readings would be helpful.