| ??? 08/23/10 13:16 Read: times |
#178240 - Several ways... Responding to: ???'s previous message |
Anita said:
I am working on a online process indicator. for its 4-20mA dc analog output, earlier I was using F-to-V , and V-to-I converters. Means the MCU will give frequency output, then through a opto-isolator it is coupled with a F to V converter and its output voltage is then converted in mA signal with a V-to-I converter stage. You could try to use one of the PWM outputs of Silabs mcu, give it through an optocoupler, lowpass filter the signal on the receiver side and convert it to 4-20mA current. But this only works if the opto is very fast and shows symmetrical propagation delay times. Of course, you can also solve the problem with the HCNR201 or IL300. Properly connected they show a superb linearity. But you might need bipolar supply voltages to make the OPamps work properly at both sides. Another option is given by Oliver. Kai Klaas |
