Electrical sending units

[hotdimmes]

I've done alot of googling but haven't really found what I was looking for...

Does anyone know how electrical sending units (pressure/temp) work as far as what they output raw? Typical output ranges? Are they linear voltages? I've seen some outputs referred to as a change in resistance. I can't find adata sheet on any brand anywhere.

 

[rollinstylee]

I'm pretty sure the sending units are resistance devices that vary based on what they're measuring (temp or pressure). Since they're usually getting the constant voltage from a 12V source, the change in resistance would alter the current going to the gauge, which is calibrated to the range of the sending unit. I think this is how they work, but if anyone knows otherwise feel free to correct me. I pondered this too when I was installing my electric oil pressure and temperature stuff. As for values, I think it depends on the make and model of gauge so you'd need to probe the resistance of the senders. What are you looking to do?

 

[hotdimmes]

What are you looking to do?

Wire sending units up to a microcontroller with general purpose IO and small display. After buying a gauge pod I started having second thoughts about how "loud" looking and attention grabbing it may be so doing this would be a fun project and a nice alternative.

 

[rollinstylee]

Cool idea.

 

[Matt R]

Yes, most are based on resistance. The Haynes manual lists the resistance ranges for most of the senders/sensors.

 

[projectSHO89]

Temperature sending units are thermistors (google that).

Pressure senders are usually either a strain-gauge that generates an output voltage based on the degree of deformation or a piezo unit that changes capacitance based on variations of pressure.

All depends on what the engineers could do with the given budget from the bean-counters.

Steve