3.5 DIGIT LCD PANEL METER, 0.2V SCALE

CAT# PM-200
$9.00 each
Quantity:  
 
Snap mounts into 2.1" X 1.5" chassis cutout. 2.65" X 1.59". No bezel. 1.84" x 0.78" display. 0.5" figure height. Operates on 9-12 Vdc.
Average Customer Review:  (8 Reviews) Write A Review

Customer Comments

Average Customer Review:  (8 Reviews) Write A Review

A customer from MOSS BEACH, CA US
Incorrect comment
This meter requires an isolated power source, not a floating one as I stated above. The meter was tested with batteries and I failed to notice that the input is fixed at about 3 volts above power negative (-). While it is the case that this can be varied, doing so causes an incorrect reading.

A customer from MOSS BEACH, CA US
Great price, does what I want
I got both this and the PM-123 LCD meter ($11.95) -- to see how each worked. --- I like this one better because its input is "adequately" isolated from the power supply such that it can be used to measure input voltages not sharing a common ground. For example you could use it with your DC power supply to measure current delivered from the positive rail, and at the same time power it from that supply. --- I haven't tested it fully but there seems to be about 10-15K resistance between inputs and power connections -- measured with a DVM and no power to the unit. I'm not sure all would be OK if the inputs were outside the power rails. Even though the price is low, I don't want to do a destructive test to see how much voltage it can take before smoking. :) I am going to get a few more for future power supply uses. --- This unit is slightly smaller in outer dimensions than the PM-128, but it appears that its LCD digits are a bit larger. The only reason I can see for getting the more expensive device is that it has a bezel that makes mounting it easier. However, if you make a cutout to exactly fit this device it snaps in place, looking all to the world just a pretty as if there was a bezel. --- The documentation for this is easier to decrypt than for the PM-128, which I am not sure I have decyphered.

Allen Gage from Houston, Texas
Really Good Cheap Meter
The documentation sucks. I've used about 100 of these meters in an application that requires read out of seconds of run duration and of grams of chemical flow per minute. I power a pair of the 200 mv model meters off a standard 12V 3-pin plus regulator with 100 mf of electrolytic cap filtering the requlator output (no ceramic bypassing), and they are very stable, acurate, and trouble free. The same PS also powers four NE-555 timers and several relays. A free floating 3V wall wart transformer supplys the measured voltage.

I made up a PC board with calibration pots to suit my application and use a standard 14-pin ladder type dip socket cut right down the middle with diagonal cutters. The meters plug right into the cut-down-the middle half dip sockets. One socket split down the middle and soldered to two different places on the meter board provides the plug in sockets for two meters.

Alternatively, one can just quick and dirty solder wires to the pins of a split-down-the- middle 14-pin dip socket, and plug the half socket into the meter. It's probably a bad idea to try to solder directly to the meter pins.

This little meter provides a lot of reliability and precision for the buck. The snap in feature is pretty crude and sloppy. Once snapped into a precision tight fit hole in a 0.060 sheet metal panel, the meters are very tricky to remove. I settled on a rectangular hole 2.225" wide x 1.490" high. That's slightly sloppy, but it allows removal without destruction. RTV can cure the sloppyness, but why bother? If a LCD segment fails, or the meter loses precision, it should be easy to snap in another meter.

A customer from Boston
Problems
I tried using this meter with a shunt together with a 20V version, both powered off a common 9V battery. Didn't work, smoked both. I had the shunt wired in the + leg of a 12V battery circuit, and the 20V meter across, so the 2 meter + inputs were common. I didn't connect the ground between the 9V meter supply and the 12V battery being metered.

I read another post online where a guy tried the same thing with the same results. He finally got things to work (with new meters) by putting the shunt in the ground leg. Perhaps that would have been a smarter way to go in the first place, but there's so little documentation with these meters it's impossible to know what will blow them up. Kind of expensive trial & error.

Nice meters, good price, crap documentation.

A customer from Somewhere
Interesting, but difficult to use
This meter requires semi-isolated power.

Basically, if you have a completely isolated power supply, the power supply rails can drift beyond the input voltage, causing the meter to error out. The resisance between the inputs and power sonnections is high enough that you have to have at least some connection between the power and inputs.

The best setup for these meters is probably a +5v -5v supply, with the power supply ground connected to the input -. If you're using the DC-32 for a power supply, use a voltage doubler on the AC outputs, and connect the centertap of the voltage doubler to the meter in- pin