Sensor testing

[spanner_monkey]

It might be something to try tomorrow.

The other two tests involving testing between the other terminals yields similarly results. Also testing various probes, new and used gives the same result. The annoying thing is that with the old meter every single test is well within specification.

[spanner_monkey]

Impedance of the meters should affect the results when testing a passive resistance also wouldnt it? This is not the case

[piratepaul]

Not necessarily, the passive is linier, the sensor is not.

When you close circuit with the meters, current is drawn, a graph of current and voltage would be less than square, a slope.
Rate of change of current is a factor in a magnetic circuit, and other nonlinier circuits.

Need spec to go further, I don't know exactly what this is.

[spanner_monkey]

Me either. My industry is not exactly forthcoming with information. Companies dont give us component specifications just overhaul and test instructions. I am hoping to get diagrams for the probes internal circuit but not much else.

[piratepaul]

Suppose you have a car, and it is parked at the top of a hill, when you take the hand break off, it rolls down the hill. Every time you do this the car reaches the same speed. If you give give it a push or hold it back speed is different.

When you close circuit with the meters, this slope is like the push...it is a big factor in the speed of the car, and a factor of your circuit.

Tell them to supply you with a meter.

[piratepaul]

Like you said in the first place, the voltage of the meters is suspect, impedance matching is a factor.
It sounds like you need to test it running at a range of frequencies.
Or on a specialist test bench at their expense.

[piratepaul]

I spoke if you put 3 meters between 3 resistors in a star with a 4th resistor from the center of the star, put all 3 meters to the end of the 4th resistor and the opposite end of the star, do it 3 times moving the meters from one resistor to the next. If the 4th resistor is the resistor being measured what result does that give.

If you use all meters in parallel directly on the resistance to be measured, the resistance or impedance of the meters is reduced, but the voltage applied to each end of the resistance is the same. Current through the resistance is increased due to meter resistance in parallel. It might fry, so you need 3 resistors in a star.

I have never tried meters in parallel but it would be interesting to find out.

[piratepaul]

That was sposed to be .....I spose. Why does it do this to me ? Why? Why?

[piratepaul]

If you use 3 variable resistors and tune them until all meters have the same reading, then do it again at a different resistance constant, hmmmm, low bat things to do back in a bit.

[piratepaul]

The solution is simple, a Wheatstone bridge, when the bridge is balanced no current flows and PD across the resistance is 0.

Tar&stuff.