question

jordanb avatar image
jordanb asked

Why are temp sensors reading too high with new Cerbo?

I installed a CerboGX about 6 weeks ago. I installed 4 temp sensors and attached them to my alternator case, MultiPlus case, and generator. They were working fine, as was the CerboGX but then something went wrong and the Cerbo was fried (long story, tl;dr incorrect voltage).

When I installed the new CerboGX, using all the existing wiring eeverything worked fine except the Temp sensors are now reading way too high.

For example, the temp sensor on the Alternator (with the engine off) used to read about 21-23C. The one on the Multiplus would read between 25C - 38C when running full power.

But now they are all reading much higher - the Alternator sensor is showing 30C and the MultiPlus sensor is showing 33C at rest and up to 52C when running full power.

I know that I can configure an offset to "calibrate" the readouts, but, I can't help thinking that something happened to the temp sensors when the Cerbo was fried, or, something is wrong with my new CerboGX because something has to explain why the same sensors are reading 30% higher than last week.

Any ideas? TIA.

cerbo gxTemperature Sensor
4 comments
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Cant really comment on the accuracy of your sensors.

But this is how I would check the accuracy / calibration of any thermometer I used.

img-20131127-160434.jpg

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Check that the wires of the temperature sensors are secure and making good contact in the terminal block of the CerboGX. It's very likely that these were disturbed when the CerboGX was replaced.

Wiggle the wire ferrules into the terminal block to ensure good contact.

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video regarding temp sensors. High voltage kiils temp sensors?

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jordanb avatar image jordanb klim8skeptic ♦ ·

Starting to sound like that's what happened. They still work, they go up and down as things warm and cool, it's just they are reading too high. Might be the chip in the sensor is damaged. So, I guess for now I will use the offset setting to bring it down into line and see how that goes for a while. Ultimately, I will have to replace the sensors.

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1 Answer
mike4nl avatar image
mike4nl answered ·

I have to say i had seen the same issue. My Cerbo GX is now 4 month old/installed and i saw also 2...4 degrees Celsius values to high aganist an industrial PT1000 control thermometer. I cheked this with the Original Sensors and my own made and there was no difference.

But now after changing my own sensors i'm able to calibrate my sensors.

I added a 10K ohm potmeter (these very small multiturn) to the sensor, calibrated him, and now my shown temperatures are correct.

When i shorten the ORIGINAL Cerbo GX sensor cable to 50 cm i get better values. Logical because the voltages are to small when you have longer cables. Now i can control the compensation in the sensor with that potmeter. Everybody who knows how top make your own sensor can do this very easy..

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