Geller Labs
Geller Labs


USB Powered Meter Tester Project



We were approached October, 2012 regarding a perceived need for a DMM reference board powered by micro USB, the theory being that micro USB powers supplies proliferate these days at both the home and work place. As the project evolved, we added some suggested alternative power options from a standard barrel connector to standard USB and solder points.

Unfortunately, this project is not a good fit for us. The desired price point was far too low to make small quantity production practical. We chose the the Linear Technology LT6654. Unfortunately the higher grade parts are too expensive for this type of low to medium precision board. Also, another design would be needed (or, an alternate pad site) for those wanting to try the ceramic part with solder balls (no smt leads).

Early prototype performance was good. For simplicity we set the boards up so one could use the reference voltage in series with the reference resistor for a crude current reference. It was understood that the relatively large voltage drop across most hand held DMMs would make the current reference aspect more an exercise in understanding the error caused by the DMM, rather than as a current calibrator. An active current source would be a far better option, however the project as is, is still over budget for where we perceive this prospective product would fit in the market place. Unfortunately, the project is already ridiculously over budget for the requested price point which would have required us to subsidize the product; not again just now, thank you!

Since we bought some parts and boards in small quantities, there will be a limited number of kits from prototype parts. These boards will be sold with all parts, except without the LT 6654 voltage reference part. They might be useful to some builders who wish to evaluate samples from LTC (no affiliation), or LT6654 volage reference parts purchased from LTC or distributors. It did turn out to be a fun little SMT kit, too bad it's so expensive (oh well).

PROJECT CANCELLED. This project has been determined to be not commercially viable.

Please be sure to do a refresh to see the latest changes

Dec, 2012 SN01 Prototype Pictures: JPG, JPG, JPG

June, 2013 SN02 Prototype Pictures: JPG, JPG, JPG (~ 6 mV drop for the mA reading)


V Reference: (Red to Black) (select only one) 1.25V, 2.048V, 2.5V, 3V, 3.3V, or 4.096V

R Reference: (Black to Yellow) 1 k 0.1%

I Reference: (Red to Yellow) {(Vref - Vammeterburden) / 1 k} mA (e.g. for a 2.5 V ref ~ 2.5 mA)


OAK - Preliminary Design

PDF Schematic Diagram

PDF Board Layout

PDF from Gerbers


JPG Earlier mock up (not current version)

Data Sheets:

HTM (1) V Reference: LT6654 1.25V, 2.048V, 2.5V, 3V, 3.3V, or 4.096V

PDF (1) R Ref: 1k Stackpole Electronics Inc RNCS1206BKE1K00 RES 1/8W 1K OHM 0.1% 1206

PDF (1) Capacitor 0.1 uf TDK Corporation C2012X7R1E104K/1.25 CAP CER 0.1UF 25V 10% X7R 0805

PDF (2) Capacitor 1.0 uf TDK Corporation C2012X7R1C105K/0.85 CAP CER 1UF 16V 10% X7R 0805

PDF (1) Resistor 10 ohms Vishay Dale 541-10ACT CRCW080510R0JNEA RES 10 OHM 1/8W 5% 0805 SMD

PDF (1) Resistor 270 ohms Vishay Dale CRCW0805270RJNEA RES 270 OHM 1/8W 5% 0805 SMD

PDF (1) micro USB B socket USB3135-30-A CONNECTOR, MICRO USB 2 , RCPT, 5POS

PDF (1) LED SML-LX1206GC-TR GREEN, 10MCD, 565NM; Bulb Size:2mm x 1.6mm

PDF (1) Resettable FUSE PTS120624V020 Cooper Bussmann PTC Resettable Fuses PPTC 120624V 0.2A SMD

PDF (1) 105-1102-001 Johnson / Emerson Connectivity Solutions Test Plugs & Test Jacks TEST JACK RED

PDF (1) 105-1103-001 Johnson / Emerson Connectivity Solutions Test Plugs & Test Jacks TEST JACK BLACK

PDF (1) 105-1107-001 Johnson / Emerson Connectivity Solutions Test Plugs & Test Jacks TEST JACK YELLOW




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