Volt-Amp Meter
I was cruising a web site and found this little meter for the amazing price of only $4.20. Such a deal, I thought. But was it? Maybe, depending on your application.
The meter reads 0-99 volts DC, and 0-10 amps DC and could be very handy if it was not for one small quirk. The sample for amperage is taken from the Negative side of the meter.
Vendor schematic of suggested hookup.
This may, or may not be a problem in your application, however it does require you to think about wire size, especially when working with a DC device drawing 10 amperes, DC.
The meter also does not have a fast sample rate, so use on something like a Yaesu FT-857D in the single sideband or CW mode would not be too helpful.
The meter seems to have about 350 mS refresh, and to be honest I was awful tempted to use a diode in place of the yellow lead and direct DC to a capacitor to stabilize the reading. That would, however, cause some errors in the readings. But maybe .1 of an amp or volt is not concerning to you.
The negative (ground) amperage measurement does rule it out for applications such as automotive, truck gear, etc. I imagine with some MacGyvering you could put it into a project box for a bench power supply, or just to monitor a power supply output. Another application could be a monitor on a solar or wind charging system, as long as 20mA doesn’t bother you when calculating losses.
The seller has these on sale at Aliexpress for only $1.88 each, and sometimes as cheap as $1.09. So maybe it’s not entirely a bad deal. They also have a voltmeter only in the same package.
Rear view of meter
Wire Connection
Seller’s Specifications on product
- Working voltage: 4.5-30V DC
- Note: The maximum input voltage can not exceed 30V, otherwise there is the danger of burning
- Working current: 20mA
- Display: 0.28″ Two color, blue & red
- Measuring range: DC 0-100V, & 0-10A
- Minimum resolution (V): 0.1V
- Refresh rate: 100mS / times
- Measure accuracy: 1% (± 1 digit)
- Minimum resolution (A): 0.01A
- Operating temperature: -15 to 70° c
- Working pressure: 80 to 106 kPa
- size: 48×29×21 mm
