Article

V & I Calibrator

Have faith in your measurements

It’s difficult to be sure that your digital multimeter (DMM) is taking accurate measurements especially if it’s a few years old. This handy calibrator gives full scale reference levels of both voltage and current, designed specifically for the scale ranges used by DMMs.
DMMs which claim to have a basic accuracy better than 1% can these days be found for less than £20. Even instruments with better than 0.5 % accuracy are selling for less than £100.

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Materials

080894-PCB.pdf

Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

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PCB

Download Gerber file: 080894-1_V11

Extra info / Update

Technical Specifation
• 0.1 % accuracy at 25°C
• Temperature stability: 50 ppm/°C
• Output voltage: 3.9 V/1.9 V switchable
• Output current: 3.9 mA/1.9 mA switchable
• Power requirements: 6 to 18 VAC or 9 V battery
• Current consumption: 5 mA

Component list

Resistors
R1 = 1k?5, SMD R1206
R2 = 3k?9, 0.1%
R3A = 68k?, 0.1%
R3B = 10k?, 0.1%
R4A = 2k?7, 0.1%
R4B = 680?, 0.1%
R5 = 1k?, 0.1%
Capacitors
C1 = 100?F 35V, radial electrolytic
C2 = 10?F 35V, radial electrolytic
C3,C4 = 100nF, SMD C1206
C5 = 10nF, SMD C1206
C6 = 1nF, SMD C1206
Semiconductors
B1 = B40S, SMD bridge rectifi er, 40V/1A
IC1 = 78L05SMD, SO08
IC2 = LT1490, SO08
IC3 = LM4050A-4.1, SOT-23, e.g. Farnell # 1468851
Miscellaneous
JP1 = 3-way SIL pinheader, lead pitch 2.54mm (0.1”) with jumper
PCB, # 080894-1