MMi203: External analog outputs
The above picture shows the connections for the two external analog outputs. They are designated analog outputs A and B. Each output can generate a 0-10V signal, with a maximum load current of 5mA, corresponding to a 2KOhm load. The outputs have internal current limiting (which is not the same as being short circuit proof!).
The analog output voltage is a positive voltage measured with respect to the 0V terminal. It is programmed using the AnOutA or AnOutB instruction. With X=0 this will result in 0V out, with X=255 it will result in 10V out.
The output resolution is 8 bits (256 steps between 0 and full scale) when you use the AnOut# instructions and 10 bits when you use fAnOut. The output is generated as a filtered pulse width modulated (PWM) signal. The filter consists of a simple 100mS RC low pass filter. For a full scale step output change, say from 0V to 10V, this will take 230mS to settle to within 10% of the full change, 450mS to settle to 1% and 550mS to settle to 0.4%.
NOTE: In the MMi200 the OBCA cannot be used in the same program as Analog outputs A and B. If you attempt to do so you will get a runtime error. Analog outputs I and J (thermistor drive and SPice connector) are not affected.
This does not affect the MMi99, MMi201 or MMi203.
How to blow up the analog outputs
Here are some ways of blowing up the analog outputs:
- Connect the output to any positive voltage over 10V and program a 0V output.
- Short the output to 0V for extended periods of time (it may survive)
- Connect the output to a negative voltage, even momentarily.