Non-contact IR temperature sensor - Analog output : Duet6XD

aOne

Hello,

I have a Duet3 6XD (not configured yet), I plan to connect a Non-contact IR temperature sensor that has 4-20mA analog output (https://www.omega.com/en-us/temperature-measurement/noncontact-temperature-measurement/fixed-infrared-temperature-sensors/oshfv-series/p/OS-HFV50-601-LT). This is for temperature measurement up to 1300 C, welding application.

My question is in two parts (sorry for basic questions: I am new to DUET and controls in general, so any help is appreciated):

Can Duet3 6XD accept analog 4-20mA in any of its IO pins? If so, is there a documentation that explains the wiring and programming of it? Can the DWC temperature chart be adjusted to show up to 1500 C? Can the temperature data be logged and extracted somehow?
What would be the best GCode syntax, to include between welding steps, so the process waits for the recently welded bead to cool down to a set point (say, 200 C) before welding the next bead? (there is no extruder heat or heater of any sort) - So will it be M109 or M116 (I don't see a syntax to define temperature setpoint using this) or something else?

Thanks very much.

dc42

@aOne 4-20mA is an old interface protocol that is not very well suited to interfacing with modern electronics. To read the output you need to connect a resistor across the output terminals and measure the voltage developed across it. Unless the negative output of the device is common with the negative power input (which does not appear to be the case for the device you linked to) then you need either to read that voltage using an isolated analog to digital converter, or use a floating 24v power supply to power it. Using a floating 24V PSU to power it, you could connect a 150 ohm resistor across the 4-20mA output terminals, also connect the negative output terminal to the ground pin of a Duet input and the positive output to an analog-capable Duet input. Then use M308 to configure a Linear Analog Sensor on that pin.

There may be a better way. That device also has TTL-compatible Tx and Rx pins. You could connect those and the TTL GND connection to a UART-capable IO port. If the TTL GND pin turns out to be common with the negative power pin then you could use a common 24V PSU with Duet VIN. You will need to establish what protocol the device uses on those pins. Other devices from that manufacturer support Modbus over TTL, but the manual for that device does not mention Modbus. I suggest you ask the manufacturer for details of the protocol, and whether TTL CND is common with 24V VIN-.

aOne

@dc42 Thanks. I spent some time searching and found out one with a thermocouple output - https://evosensors.com/products/close-focus-small-spot-size-infrared-temperature-sensor-with-dual-laser?_pos=1&_sid=745f48207&_ss=r. Do you think, using the daughter board on the duet, this could be an easier connect than the one I asked about earlier, as this could be a straightforward connection?

Also, would love your opinion on my question 2 from before, if I configure the sensor using your Voltage or UART suggestion.

dc42

@aOne are you certain that it has an output that emulates a thermocouple? Something to watch out for is that the thermocouple daughter board is designed to work with isolated thermocouples, and if that sensor does provide a thermocouple-compatible output then it is unlikely to be isolated.

Here's one that provides Modbus output: https://www.calex.co.uk/product/temperature-measurement/infrared-temperature-sensors/pyrominibus/. Note, we don't currently support Modbus devices directly as sensors although I am likely to add this support soon. Meanwhile they can be read using M260.1 commands.