Hi,
My current project includes some Amploc AMP25 hall effect current sensors: AMP25 Open Loop Hall Effect Sensor – Amploc
These are being read by analog pins of a 5V pro mini.
The sensors are reading automotive non-reversing DC air compressor motor current, nominal 28A, peak of around 40A at startup. My goal is to monitor the current to confirm running and monitor their general health, so I think even a 1/2 amp resolution is more than enough.
As the sensors can read positive and negative current, 0A (null) outputs supply voltage /2, and will decrease towards 0V for negative current or increase towards 5V for positive current at the rate of 37mV per amp sensed. In my case: 2.5V + (40A*.037A) = 3.98V So my sensor output should swing from 2.5V to 3.98V for a 0-40A current flow.
If my math is correct, with a 10-bit analog input, that works out to around a 0.13A per bit resolution. While that is enough for my needs, I'm concerned about the signal jumping around due to noise. I'm thinking I should offset the signal down and expand it?
You can implement an averaging technique in your code to smooth out the sensor readings. By taking multiple readings and averaging them over time, you can reduce the impact of momentary noise spikes. The number of readings to average can be adjusted depending on the desired balance between responsiveness and noise reduction.
Hi barshatriplee,
I'm familiar with that technique, thanks.
I was trying to decide if it makes sense to expand the signal electronically prior to hitting the analog pin.
Let's assume zero current results in ADC value of 511, and 40A (3.98V) results in 814. 814 - 511 = 303, 40A / 303 = 0.132A per ADC count.
How many counts does the ADC output jump around?
Sorry, maybe I wasn't clear.
I don't have the sensors yet, they are on order. I have not trialed the circuit yet.
My question was more about how to approach the connection.
As my application would only use about 30% of my analog input range, I could either:
A) Directly connect the sensor an run it as-is
B) Expand the signal electronically to use more of the analog input range.
As .132A per count is plenty of resolution, it sounds like keeping it simple with a direct connection is the way to go.