FAQ
TL;DR: After a 2-minute trim the Chinese 0-100 V / 0-10 A panel meter reaches ±2 % accuracy [Elektroda, koala106, post #17118384]; “worth the money” [Elektroda, h3c4, post #17117098] Calibrate two onboard trimmers, mind a 75 mV shunt, avoid reverse polarity. Why it matters: A €2 gadget can become a trustworthy lab readout when you know its limits.
Quick Facts
• Measurement range: 0–100 V DC & 0–10 A DC [Elektroda, CMS, post #17116791]
• Power requirement: 4–30 V, ≥100 mA [Elektroda, CMS, post #17116791]
• Typical post-cal accuracy: ±2 % of reading [Elektroda, koala106, post #17118384]
• Cost at purchase: PLN 6 (≈ US $1.70) [Elektroda, CMS, #17116791; mariomario, #17117318]
• LED lifespan: some fail after 6 months, others run 3 years 24/7 [Elektroda, h3c4, #17117098; jousto, #17117168]
What are the official voltage and current limits of the meter?
The module reads 0–100 V DC and 0.01–10 A DC. Seller notes usable accuracy starts above 1 A, yet the display activates at 0.01 A [Elektroda, CMS, post #17116791]
How do I wire the three- or five-lead version correctly?
- Connect thin red to +V supply (4–30 V).
- Connect thin black to supply ground; leave floating if supply equals measured source.
- Route load current through the thick red (+) and thick black (−) leads.
- For separate voltage sensing, attach thin yellow to the point you want measured [Elektroda, CMS, post #17116791]
Can it measure negative voltage or bidirectional current?
No. The standard board is unipolar; reversing polarity shorts the internal supply and may destroy the meter [Elektroda, Anonymous, post #17119702] Some variants simply read 0 A/0 V when reversed, but still only one direction is measured [Elektroda, Anonymous, post #17119702]
How accurate is it out of the box?
Users report errors of 20–40 mA at 300 mA and 0.04 A at 1 A [Elektroda, CMS, post #17116791] Larger currents deviate 5–10 %. After trimmer adjustment, several units matched a Metex DMM within ±2 % [Elektroda, koala106, post #17118384]
How do I calibrate the displays?
- Power the module and connect a precise DMM in parallel.
- Use a small insulated screwdriver to turn the VOLT trimmer until both meters match.
- Repeat for the AMP trimmer while passing 5 A through the shunt.
The entire process takes under three minutes [Elektroda, CMS, post #17116791]
Why does the ammeter read low on battery chargers or thyristor rectifiers?
The current waveform is pulsed; the meter averages it poorly, causing readings 40–50 % low above 2.5 A [Elektroda, kot mirmur, #17129541]. Adding a 10 µF–4700 µF filter across the LM358 input improves accuracy but may upset charger control [Elektroda, kot mirmur, #17146760].
What wire or shunt size is safe for 8 A continuous?
Replace the stock 0.2 mm² leads with 1.5 mm² copper; originals overheat and melt at 7 A [Elektroda, mariomario, #17119795; koala106, #17120194]. Keep lead length short to limit voltage drop to <50 mV at 8 A.
My board arrived without a shunt and shows 52 A at idle—what value do I need?
Solder or bolt in a 0.0075 Ω (75 mV @ 10 A) resistor for a 10 A range. For 20 A use 0.00375 Ω, for 50 A use an external 75 mV/50 A block. Without the shunt the op-amp saturates at ~52 A reading [Elektroda, mumotg, #19938992; Szyszkownik Kilkujadek, #19938184].
Do the LED segments really burn out after months?
Mixed results: one user lost segments after six months [Elektroda, h3c4, post #17117098], yet another runs the same model 24 h/day for three years with no dimming [Elektroda, jousto, post #17117168] Lowering supply voltage to 5–7 V reduces stress and heat.
What happens if I reverse the current leads?
The meter shorts its internal 5 V regulator and can fail instantly; at minimum it shows 0 A [Elektroda, CMS, #17116791; Anonymous, #17119702]. Always observe polarity or add a series Schottky diode as cheap insurance.
Is there a larger or more feature-rich alternative?
Yes. Models like D85-3051AG (0–200 V/50 A) have bigger digits and store calibration; price ≈ PLN 30 [Elektroda, M.R-V4, post #19361005] KWS-DC200 versions add power (W) and energy (Wh) display after minor calibration [Elektroda, M.R-V4, post #19361472]
Can the meter display accumulated energy (Wh)?
Not the basic 3-digit unit. Choose a KWS-DC200 or similar; it integrates voltage and current to show amp-hours and watt-hours, resettable via front button [Elektroda, M.R-V4, post #19361472]
