Temp Sending units for engines

[aarotech]

I have an engine that has water temp, hydraulic temp, lube oil temp and trans temp. These are all installed with sending units that have been matched to the gauges. I want to hook up a PLC with a HMI to read these levels. Do I have to have seperate thermalcouples or rtds or can I use one signal for two inputs?

 

[dknguyen]

I have an engine that has water temp, hydraulic temp, lube oil temp and trans temp. These are all installed with sending units that have been matched to the gauges. I want to hook up a PLC with a HMI to read these levels. Do I have to have seperate thermalcouples or rtds or can I use one signal for two inputs?

You'd have to separate them since they use require different circuitry and processing anyways if you were connecting the TC and RTDs directly.

But, you say sending unit. What's a sending unit? Something that processes the sensor readings and sends out a digital signal? You could share them if they used a serial protocal that allowed for networking/addressing.

 

[aarotech]

Impedance matching

These meters and the Temperature sending unit are impedance matched at the factory.

 

[dknguyen]

What does a sending unit *do*?

 

[gerty]

A sending unit is the sensor that monitors temp, pressure,etc..
They usually are a varying resistance for gauges ,or a set of contacts for a indicator light.
I'm no authority but I think if you try to tie the gauges to the plc via sending units, neither will work properly.

 

[Externet]

Hi.
You should be able to read the existing sending units with your second PLC-whatever circuit paralleled to them if its input channels resistances are high enough (like 1mΩ?)
Miguel

 

[3v0]

I think each automaker may have different specs for their sending units (sensors). You need to search for info specific to the make and maybe model of car you are working with.

This is about temperature and fuel tank sensors.

If you want to get better help here you need to tell us exactly what you are working with.