Product Overview
3.5-Digit Dual-Slope LCD Voltmeter Module with Selectable Decimals
Condition
New old stock. Unused 3-1/2 digit LCD panel meter assembly with rear threaded mounting posts. Circuit board carries Kai Fu FR-4 silkscreen. Includes manufacturer PM128/PM-188 technical instruction sheet.
Same or next business day shipping from our Idaho warehouse. Reliable parts since 1999. Honest pricing, no nonsense.
We are here for our customers, with a no-hassle satisfaction guarantee.
Product Overview
Engineered for clean instrumentation readouts, the C+C PM128 digital panel meter provides direct DC voltage measurement up to 199.9 mV full scale. Built around a dual-slope integration analog-to-digital converter, the module features a 13 mm figure height reflective LCD display with automatic polarity indication and selectable decimal point positions. Configurable via onboard solder jumper pads, it operates from an isolated 9V DC source with 1 mA nominal current draw, making it suitable for custom bench supplies, process monitoring, and dedicated instrumentation displays.
Key Features
- 3-1/2 digit reflective LCD readout with 1999 maximum display count and automatic polarity indication
- 13 mm (0.5 in) figure height for clear viewing
- 200 mV DC basic full-scale input sensitivity with input impedance exceeding 100 MΩ
- Dual-slope integration A/D conversion with 2 to 3 samples per second
- Selectable decimal points via onboard solder pads (P1, P2, P3, N)
- 9V DC nominal operating voltage (7V to 11V DC range)
- Front-bezel snap-in design with rear threaded mounting studs
Applications
- Adding a dedicated voltage readout to a custom linear bench power supply build
- Integrating into an analog equipment retrofit to display shunt voltage drops or current monitor signals
- Monitoring isolated sensor transmitter outputs in prototype lab setups
- Building low-power portable field instruments operating on standard 9V battery power
Frequently Asked Questions
Can the meter share the same power supply as the circuit being measured?
In standard 200 mV configurations, this meter requires a power supply isolated from the input measurement signal. Sharing common ground between the 9V supply terminals and the measurement input (VIN/GD) can lead to erratic readings or damage to the dual-slope converter. A dedicated 9V battery or an isolated DC-DC converter is standard practice.
How is the meter configured to read voltages higher than 200 mV?
Measuring higher DC voltages requires adding external scaling resistors to form a voltage divider across the designated RA and RB circuit board pads. Solder bridges at pads P1, P2, or P3 activate the corresponding decimal point on the LCD screen to match the chosen measurement range.
What distinguishes the PM128 module from the PM129 series?
The PM128 utilizes a reflective LCD display suited for ambient light conditions and low current consumption, while the PM129 series uses an active LED display requiring significantly higher supply current. Both share the standard front bezel dimensions and dual-slope converter architecture.
Before everything moved to microcontrollers and serial buses, clean panel readouts relied on dual-slope converters and dedicated glass. Wire in your divider, set the decimal jumper, and let your custom bench build do the talking.
