Voltmeter calibration

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cwah   10 GW

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Voltmeter calibration

Post by cwah » Jun 13 2018 2:24pm

Hello

I bought this and it's quite nice:
http://s.aliexpress.com/yiYfueqy

However the power shown seems a bit out of whack. How can I calibrate voltage and ammeter correctly? Is there something I can buy to find out what the proper voltage and power usage of my set up is?

Thanks
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

Addy   100 W

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Re: Voltmeter calibration

Post by Addy » Jun 13 2018 2:36pm

Are you able to pop the back of it off? A lot of these small voltage/current displays have potentiometers inside which you can adjust to calibrate the voltage or current readings. You could calibrate it using a multimeter, for example by measuring something with your aliexpress meter and the multimeter at the same time, and adjusting the aliexpress meter until the display matches what the multimeter says.

cwah   10 GW

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Re: Voltmeter calibration

Post by cwah » Jun 13 2018 3:07pm

I think it's possible to do it with the settings. I think I can calibrate voltage with voltmeter however I don't know how to calibrate power with that?
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

Addy   100 W

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Re: Voltmeter calibration

Post by Addy » Jun 13 2018 3:11pm

Power is a calculated value, it's voltage multiplied by current. If you calibrated the voltage and current values, power would be calibrated too.

cwah   10 GW

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Re: Voltmeter calibration

Post by cwah » Jun 13 2018 3:21pm

Yes but how do I calibrate current value?
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

Addy   100 W

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Re: Voltmeter calibration

Post by Addy » Jun 13 2018 3:46pm

Measure some current with your aliexpress meter. For example, you could hook up a 12V battery with an automotive light bulb so you have some current flow to measure. Then all you need to do is hook up the multimeter in series with your circuit so you can see the measured current on both meters at the same time.

It would be best to calibrate the aliexpress meter with some current that is close to what you would normally be measuring. If you calibrate the meter at 1A, but you're normally measuring around 30A, your meter might still be inaccurate at that range.

I haven't used this specific meter that you're asking about, but the other cheap meters I've used are usually not very accurate. You can calibrate them at a specific value, but the further away from your calibrated value you go, the less accurate the reading is.

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ddk   1 MW

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Re: Voltmeter calibration

Post by ddk » Jun 13 2018 4:49pm

That type of meter has a setting for a 50A shunt or a 100A shunt. I have a half dozen of these and several were set for the 50A shunt even though I had 100A shunts... lol
thru me a loop-de-do for a bit

I have a "manual somewhere around here and will look for it... maybe.

As for the meter's overall accuracy, well, I only care about the watts used and the meter is 'close enough' for guessing when to recharge.

BTW you reset the watts by holding down the 'set' button until CLR is displayed then push the button one more time to clear the watts readout.
"How can we play Hot Wheels without lighter fluid? " -Serge

cwah   10 GW

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Re: Voltmeter calibration

Post by cwah » Jun 13 2018 4:57pm

Thanks I've looked at a video and it seems to make sense how to measure current:
https://youtu.be/P660hTqkGiY

I do not want to disassemble my bike just to measure current.

Is it possible to put my voltmeter in series with my battery? It's 60v. Then I can just turn on the light. I'm a bit concerned of spark when I'd use the 2 probe to close the circuit
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

dustNbone   10 kW

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Re: Voltmeter calibration

Post by dustNbone » Jun 13 2018 4:57pm

I have one of the same meters, and it's shockingly accurate against my Fluke meter. The current (with a 50A shunt) was within .05A every time I checked it, and the voltage was close enough to spot on for any variance to be inconsequential.

Not saying they're all like that, but all told a lot more than I expected for a few bucks.

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ddk   1 MW

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Re: Voltmeter calibration

Post by ddk » Jun 13 2018 5:49pm

cwah wrote:
Jun 13 2018 4:57pm
Thanks I've looked at a video and it seems to make sense how to measure current:
https://youtu.be/P660hTqkGiY

I do not want to disassemble my bike just to measure current.

Is it possible to put my voltmeter in series with my battery? It's 60v. Then I can just turn on the light. I'm a bit concerned of spark when I'd use the 2 probe to close the circuit
You only need to insert the shunt (the big rectangular thingy with two bolts) in the POS battery lead. The meter can be wired "on", with the backlight turned off where it then draws insignificant current. You turn the backlight on/off by momentarily pressing that one-and-only 'set button' If you disconnect the battery the meter remembers the watts- The reason why I use this meter!
I left a meter connected to a 5A battery for over a year and the battery still needed no recharge (sez something about lithium self discharge :wink: )
And as said before, the voltmeter portion is as accurate, or more so than most other small meters
of similar types. That is- once you set the shunt for the one you have lol

Do note that this meter is NOT waterproof.
I build them into my battery cases which is why I have so many.
"How can we play Hot Wheels without lighter fluid? " -Serge

cwah   10 GW

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Re: Voltmeter calibration

Post by cwah » Jun 14 2018 6:28am

Thanks will do. I don't have this voltmeter but I have another cheap one similar. Will post if it doesn't work out
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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