fieldpoint controlling heater pwm vs digital potentiometer

[Monse]

Hello,

I'm looking for some advice on how to control a heater... I have a 82ohm heater which I need put between 0-40V across it, and control this voltage using labview... I have several analog out and digital out fieldpoint modules... at first, my idea was to use my digital out module with a digital pot and using an adjustable voltage regulator, control my voltage.... but I haven't been able to find a digital pot that can take 40V... so, I'm thinking about PWM.... but I've never used PWM before and this is where my question is....

is it possible to use fieldpoint modules to create a PWM signal that can drive a heater?

much thanks!

[Stephen_S.]

Hi Monse,

What digital output module are you currently using, and how are you getting the voltage up to 40 V? We do have a PWM module, but the maximum output range is 30 V. Also, if I am understanding you, you just want to be able to output a voltage and control the level of the output. The easiest way to do this is to us an analog input, but there are still no modules that will output 40 V.

Give some more information about your system, and what you are doing as far as external circuitry.

Regards,

Stephen S.

[nathand]

Omega sells a PCM4 module that takes a 4-20mA signal and produces a PWM output that you can use to drive a solid state relay, which you can then use to switch your 40V supply.  It should not be hard to find an appropriate relay, and the PCM4 module mounts directly onto the relay so it's easy to install.  Of course you will need to use a Fieldpoint analog output module that outputs current, not voltage.

Message Edited by nathand on 05-06-2009 03:34 PM