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Author Topic: "Doc Wattson" R102 DC Ammeter & Amp Hour Meter  (Read 14412 times)

Offline tak22

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"Doc Wattson" R102 DC Ammeter & Amp Hour Meter
« on: November 16, 2010, 06:35:37 PM »
Does anyone have any experience with the battery monitors from RC Electronics? Would they give accurate measurements or would they be 'fooled' into giving false readings when used for measuring inputs/outputs for small OU projects? All opinions appreciated.

tak

http://www.rc-electronics-usa.com/ammeter-simulator.html

Measures DC Amps, Amp-hours, Watthours, Volts and Watts

Captures peak current, peak power, and minimum voltage (voltage sag) lasting a fraction of a second.

Easily reset accumulated readings using external pushbutton switch.

Rare combination of Voltmeter, DC Amp meter & Amp hour counting, Watthour and power analyzer features. Measures wide range of values not normally found on multimeters or low cost test equipment

Powered by the measured circuit or connect an auxiliary battery or DC power source to provided 3-pin socket

Reverse connection protection

Powerful, 8 MIPS micro-controller

Factory calibrated with constants stored in EEPROM. No pots to drift

Uses very low resistance (0.001 Ohm) shunt in negative (black wires) leads



Offline CTG Labs

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Re: "Doc Wattson" R102 DC Ammeter & Amp Hour Meter
« Reply #1 on: November 16, 2010, 07:11:59 PM »
I have a similar one.  It doesn't register any current unless the current is >1amp and it can only do DC.  It can only be used on steady DC voltage/current devices and is useless for anything else I am afraid and certainly not for testing noisey OU devices.  A decent digital oscilloscope with math functions is really the only way to go if you want real average power measurements.


Regards,

Dave.

Offline poynt99

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Re: "Doc Wattson" R102 DC Ammeter & Amp Hour Meter
« Reply #2 on: November 16, 2010, 07:12:51 PM »
tak22,

I would set up a test.

Pulse-drive a resistive load and use the meter appropriately to get the current and voltage readings. Use 50% duty cycle to keep things easy to calculate and start off with a 60Hz square wave. Take your readings and monitor while increasing the frequency up to 100kHz or so. See how much the readings deviate from the initial reading.

You could also try varying the duty cycle and see how well it follows. I suspect this meter will give poor results at anything higher than a few kHz (if that) as the A/D sample rate is probably quite low.

.99

Edit: Well there you go, as per Dave's post above, the unit appears useless for pulsed-DC measurements.

Offline tak22

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Re: "Doc Wattson" R102 DC Ammeter & Amp Hour Meter
« Reply #3 on: November 16, 2010, 07:48:50 PM »
Thanks for the replies on pulsed applications, that's kinda what I thought would happen.  :)

How about DC applications like charge and discharge of capacitors, both slow and fast,
to and from batteries? Seems there's always a new capacitor mystery popping up. :)

How about earth batteries?

Dave,your similar device doesn't start measuring until > 1 amp, but this one lists .01 Amp resolution. You have the exact same device? Maybe this is the resolution after a min threshold?

It just looks so attractive for quick low power DC testing of near random ideas....  ;D 

tak




Offline CTG Labs

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Re: "Doc Wattson" R102 DC Ammeter & Amp Hour Meter
« Reply #4 on: November 16, 2010, 08:00:35 PM »
Hi,

I am at work right now so I can't look at it, but the one I got is this one http://www.rcmodelcentre.co.uk/RC-Watt-Meter/prod_616.html

I believe it said it could read current below one amp, but what I found was that it would only display the voltage and the current would only show up when it was over an amp.  The watts would not display either because there was no current do multiply with the voltage.  So I was not very pleased with it.


Dave.

Offline tak22

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Re: "Doc Wattson" R102 DC Ammeter & Amp Hour Meter
« Reply #5 on: November 16, 2010, 08:46:24 PM »
Thanks Dave, I looked that one up and it's quite limited compared to the Doc Wattson and it has a minimum input of 3.3 volts which probably explains the 1 amp minimum. Here's a sample spec link for it:

http://www.4-max.co.uk/pp-wattmeter-n.htm

tak