#181 DC Voltmeter Modules
Testing a selection of 3-wire DC voltmeter modules.
Notes
There are two and three wire DC voltmeter modules in the market.
Two-wire modules are the simplest (and generally cheapest). For most applications where a simple readout of a power supply is required, they are most convenient since a separate power supply connection is not required. It does mean of course that the meter draws current from the circuit under test, and will only work down to a certain voltage (usually ~4.5V).
For more precision measurement, the three-wire modules are better suited:
- they present relatively high input impedance (> 100kΩ)
- can measure voltages from 0V and up
Modules tested below:
- Module 1: DSN-DVM-368 v3.01. Screw mounted with no bezel, measures from 0-30V
- Module 2:
Test Circuit
Schematics below are for a simple test of the meter using a 10kΩ pot to vary the input voltage and compare the reading with a multimeter.
NB: the Fritzing part used here is not quite right (it’s actually a 4-wire ammeter) but does well enough for a simple schematic:
Module 1: DSN-DVM-368 v3.01
This is a common type of module that is screw mounted with no bezel and can measure from 0-30V.
I think I originally obtained this module as part of a kit, but they are widely available from parts sellers:
- DSN-DVM-368L-3 3-Digit 0.36” LED Digital DC Voltmeter - example product listing on dx.com
- Mini DC 0-100V Yellow LED 3-Digital Display Voltage Voltmeter - example product listing on aliexpress
I can’t find a specific datasheet for the module, but from product listings, the specifications are as follows:
- Measuring range: 0~30V;
- Power supply: DC 4.5~30V;
- Max. input: DC 30V;
- Tolerance: +/-1%, +/-0.3V (>=10V), +/0.1 (<10V);
- Input impedance: >100KΩ;
- Working current: red: <23mA;
- Refresh rate: 300ms;
- Display: 3-digit 0.36” LED;
- Display color: red;
- Cable length: 15cm
These modules do not have any kind of digital output that could be used to integrate with a microprocessor, but as a stand-alone meter, a useful device for power supply circuits.
Using my DMM as a reference, it appears accuracy is within 40mV, good enough for general purposes.
Module 2: 0.56” Panel Meter
This is a common panel mount module with 0.56” digits and can measure from 0-100V. Other versions are available with different measurement ranges: 0-10V, 0-30V, 0-200V.
They are widely available from parts sellers, e.g.:
- 0.56” 3 Wire Digital LED Voltmeter Voltage Meter Panel with Reverse Protection DC0-100V (Red) - aliexpress
I can’t find a specific datasheet for the module, but from product listings, the specifications are as follows:
- Test voltage range: DC 0-100V
- Accuracy: 1%
- Display: 3 digits LED
- Working temperature: - 10 ~ + 65℃
- Measurement rate: 200mS/time
- Power: DC 3-30V
- Max. output: DC 100V (above 100V carries a risk of burning)
- Min. output: DC 0V (Below 0V, measurement inaccurate or not shown)
- Current consumption: <20mA
- LED color: Red/Blue/Green/Yellow (Optional)
- Weight: Approx.17g/0.6oz
- Size: Approx.4.82.91.9cm
Tests reasonably accurate:
