Sensor Loading

Thread Starter

Teszla

Joined Jun 7, 2013
43


Could someone help me how to calculate this (Example 9.1). First I wonder, which variabels will be the same in both cases? K is supposed to change with 0.1 percent, meaning that K2 should be 1.001*K1 (or 0.999*K1? How should we know?)

How would you calculate this? Is this even a realistic example?
 

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Thread Starter

Teszla

Joined Jun 7, 2013
43
What I don't understand is how we should know if the sensitivity constant is changing to become 0.1 percent bigger or 0.1 percent smaller?

Also, wouldn't Vin be different in each case?
 

#12

Joined Nov 30, 2010
18,167
First, loading a sensor is going to reduce a positive voltage from the sensor.
You can make an equivalent circuit as a voltage divider and adjust the load on the sensor until 5 volts droops to 4.999 volts. Rule of thumb is that the load must be 10X the sensor's internal resistance to load it by 10%, 100x > 1%, etc.

The sensitivity of the sensor is not changing. The sensitivity of the system is changing. The internal resistance of the sensor is changing. Is the change just something the author contrived or is the change what we are measuring to find the data? Doesn't matter. All you need to find is, "What load will not throw the data off by more than .1%?"
 
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