I have read that VCOs can be a simple and cheap way to digitize sensor data and send them over relatively long distances. I like the concept but I haven't read anything on such a setup providing isolation.

Any thoughts and ideas on this?

 

What is a VCO?

 

VCO is normally used for voltage controlled oscillator. I would normally expect to see one in an ANALOG circuit.

To digitize ANALOG sensor data you would use Analog to Digital Converter, commonly abbreviated ADC.

 

actually what you are needing is a voltage to frequency converter.similar to a vco, but optomised for telemetry.

 

As regarding isolation, that may or may not be required, depending upon the application. Typically the signal is not isolated, but if required, you can use an isolator such as an opto coupler for the digital signal output from the sensor to the receiver.

 

I have read that VCOs can be a simple and cheap way to digitize sensor data and send them over relatively long distances. I like the concept but I haven't read anything on such a setup providing isolation.

Any thoughts and ideas on this?

Perhaps you mean voltage to frequency converter in one end and the reverse in the other end. A typical circuit for this was this one. http://www.ti.com/lit/ds/symlink/lm231.pdf They also make an IC to match the function in the other end (dont remember the name) The IC was popular before micocontrollers took over such functions

 

It's commonly done in industry, as a frequency signal can be very reliable over long distances.

It's also common in sensors. A lot of the light sensing and colour sensing ICs have frequency output.

 

Perhaps you mean voltage to frequency converter in one end and the reverse in the other end. A typical circuit for this was this one. http://www.ti.com/lit/ds/symlink/lm231.pdf They also make an IC to match the function in the other end (dont remember the name) The IC was popular before micocontrollers took over such functions

This exactly what I was looking for. Very much appreciated.

 

As regarding isolation, that may or may not be required, depending upon the application. Typically the signal is not isolated, but if required, you can use an isolator such as an opto coupler for the digital signal output from the sensor to the receiver.

Any recommendations on an octocoupler that would be able to work with the mentioned voltage to frequency LM231's operating temperature of -25C to 75C or 85C?

 

Another question, I need to sense overcurrent and trigger a contractor to open. Normally the contractor is normally open for safety releasing but kept open via PWM control signal.

Any ICs available that can do current detection via differential voltage across a shunt and trigger a control to a contractor? Assuming the current needed for the contractor comes from a separate source.