I have eight remotely-mounted thermistors that are part of an air handling unit (two units, actually). We have replaced the old Delta Control units with a PLC that we can program & troubleshoot in-house. Outside air and room temperature sensors are RTD type, but I just realized that sensors internal to the AHUs are thermistors.
I know I can use a universal signal conditioner to change the thermistor "signal" to a 0-10V or 4-20 signal, but I would need eight of them.
I'm hoping someone knows of a multi-channel thermistor input device capable of modbus communication.
Also, I've had good results in a previous project where I used one available 0-10V input point to connect to several RTDs using an eight-point relay output card. I'm wondering if, perhaps, I could do the same sort of thing with a single signal conditioner. The original project didn't require rapid response, so I would cascade through the relay outputs, one at a time, holding each closed for 10 seconds. All output COM were connected together and were connected to the universal signal conditioner. The last reading was considered "good" and was maintained until the next cycle, 60 seconds later.
I know I can use a universal signal conditioner to change the thermistor "signal" to a 0-10V or 4-20 signal, but I would need eight of them.
I'm hoping someone knows of a multi-channel thermistor input device capable of modbus communication.
Also, I've had good results in a previous project where I used one available 0-10V input point to connect to several RTDs using an eight-point relay output card. I'm wondering if, perhaps, I could do the same sort of thing with a single signal conditioner. The original project didn't require rapid response, so I would cascade through the relay outputs, one at a time, holding each closed for 10 seconds. All output COM were connected together and were connected to the universal signal conditioner. The last reading was considered "good" and was maintained until the next cycle, 60 seconds later.
