Just acquired what might be the smallest voltmeter ever. See photo. It's the DLP-PMV by DLPDesign of Texas. Only costs $18.00  Will measure AC or DC up to 60V. Neat for bringing to club meets to check transformer and power supply voltages. 
MINIVM11.19

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That's about 99% useless for all around work.  Much better for half the price, $8.88 shipped free from a US seller. 

eBay: 271496690158

 

000

Even the free one from Harbor Freight is far better.

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hokie71 posted:

That gizmo is neat but a solution looking for a problem as far as my feeble brain can figure. I vote for the $9 GRJ item for functionality!

My thoughts exactly.  Someone just figured they'd capture the gadget guys with a unique toy.  This is the Pet Rock of multimeters.

Consolidated Leo posted:

"Protometer" is just the name of the product (a registered trademark). It can be hooked up to a USB port for data logging. Pretty neat!

There seem to be a number of versions. Here's a link to a pdf:

https://www.dlpdesign.com/DLP-PMV-V10.pdf

Too harsh replies I think...

Actually it seems to have a specific purpose, namely breadboard use. It seems great for that, rather than fussing with a meter that wants to lay flat and probes that won’t fit in breadboard holes. Could use MA and OHMS though.

Chuck TCA LCCA ARRL BMWMOA

cjack posted:

Too harsh replies I think...

Actually it seems to have a specific purpose, namely breadboard use. It seems great for that, rather than fussing with a meter that wants to lay flat and probes that won’t fit in breadboard holes. Could use MA and OHMS though.

That was sort of my thought.

Probably not too useful for general use with trains (since you obviously have to transition those 2 pins to some sort of alligator clip or banana jack to measure a transformer or track).

But if someone is building a circuit and wants to monitor voltage at  a certain point (and possibly log it to a computer - while I didn't read the datasheet details, it says it can log via a USB port), it might be useful.  Can't log to a USB port with the $8 Harbor Freight models

It also frees up 2 of the banana jack posts on your proto board if you don't have to waste them on a voltmeter just to transition from probes to wires that fit in the proto board holes.

-Dave

Certainly you wouldn't want this little gadget to be the only VOM in your toolbox. But for bread board testing it could come in handy. I can think of a number of situations where you might want to log some readings to a computer for time based applications. I'm just going to keep this in the back of my mind if such a need ever occurs.

I have three of those Harbor Freight digital voltmeters , a Radio Shack analog multimeter and a Triplett. I use them all. The DLP's shirt pocket size makes it handy to bring to other locations like club meets. It's primary focus is to test voltage on two adjacent pins in a PC board. It also has a USB port for logging voltages. For general use, I rigged a clip lead that plugs in (photo). Not exactly a breakaway product, but kind of neat and it's accurate.

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Well, I'd even yield the point on data logging, but the information of how to actually do that is, shall we say, sparse!  There is no information on the data format, but a mention of an optional USB cable.  When you go to their site, and I'll be dipped if I can find any more information about the mystery USB cable or the data format from this device.  Given that data logging seems to be elusive, to say the least, I'd pick something more capable and small

A unit like this is WAY more flexible and capable.  If you're willing to go overseas, similar items start around $10.

Dawson Tools DDM190 Pen-Type Digital Multimeter,$26.55

Features
• LCD Display
• Auto-ranging
• Auto Power Off
• Diode Test
• Audible Continuity
• Max Display
• Non-Contact Voltage Detector
• Data Hold
• Retractable Tip
• Low Battery Indicator Measures: AC/DC Voltage
• Resistance Safety Rating: CAT. II 600V Specifications
• Auto and Manual Ranges
• Max. Voltage between Terminals and Earth Ground: 600V DC or AC
• Maximum Operating Altitude: 7000 Ft (2000m)
• Display: 0.79 In. (20mm) LCD
• Maximum Number: 1999
• Polarity Indication: ‘-’ Indicates negative polarity.
• Overload Indication: Displays ‘OL’
• Sampling Time: Approx. 0.4 second/time
• Low Battery Indication: “ ”
• Auto Power Off: 15 min
• Power Supply: 1.5V × 2 AAA battery
• Operating Temperature: 32°F To 104°F(0? To 40?)
• Storage Temperature: 10°F To 122°F(-10? To 50?) Accessories
• Test Leads
• Alligator Clip & cable
• 1.5V AAA Battery
• Case
• Test Leads
• Alligator Clip & Cable
• 1.5V AAA Battery
• Case
• User’s Manual

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With regard to the data logging feature, they mention 9600 baud N81 (no-parity, 8 bits, 1 stop bit) ASCII with CR/LF. Pretty standard way to transmit values.

Also found some software on their web-site for drivers and utilities that may be of use. It's not hard to write a program that will read data from a USB port.

These are free downloads that I did not install or test. I'm not sure why you would want to download drivers from here. USB drivers are already on most PCs already. An old style terminal emulator (like "teraterm") is configurable for USB serial data.

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I suppose you can conceive of a use for doing the work to figure out the logging, but I can assure you that 99.9% of the folks here looking for a multimeter function would be far better served with one of the many similarly priced choices for full function multimeters. 

I saw all the choices of drivers, etc., but real information was certainly lacking.

Leo, I think we should agree to disagree about this one.

gunrunnerjohn posted:

… I'll be dipped if I can find any more information about the mystery USB cable

My guess is the cable is a more than a connector and wires...maybe something like this FTDI converter for 3V RS-232 to USB.  There's a microcontroller chip inside the molded USB connector and wire-ends on the voltmeter side as suggested in their photo.

ftdi 3v usb rs232 cable

The "cable" costs as much as the voltmeter itself! 

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harmonyards posted:

Just out of curiosity, nothing more......what in the world would you data log on a model railroad? ........Pat

You could attach this device to track power and monitor what happens to the voltage as your train goes uphill/downhill, pulls additional weight, anything that occurs over time.

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