Terminal Inter Lock Digital Multimeter ( HTC – DM-91 )

Description

The HTC DM‑91 Digital Multimeter is a robust and versatile 3½‑digit manual-ranging instrument offering 1,999‑count resolution, ideally suited to technicians, engineers, and electronics hobbyists. Designed to combine precision and reliability, it measures a comprehensive range of electrical parameters—including DC/AC voltage and current, resistance, capacitance, frequency, diode testing, transistor hFE, temperature, and IR signal detection—with overload protection across all ranges, under IEC‑1010 CAT II safety standards.

Equipped with wide-ranging DC voltage capabilities, the DM‑91 covers 200 mV to 1000 V DC, offering resolution from 0.1 mV up to 1 V. Accuracy is specified at ±0.5% of reading ±1 digit in the 200 mV range, ±0.5% ±3 digits in low-voltage ranges, and ±0.8% ±3 digits at 1000 V. It also includes a 10 MΩ input impedance and built-in overvoltage protection, making it ideal for both professional and everyday use.

AC voltage measurement extends up to 700 V AC, with a resolution of 1 mV to 1 V depending on range. Accuracy ranges from ±1.0% reading ±5 digits at lower ranges to ±1.2% ±5 digits at 700 V. Measurement is AC RMS‑based (averaging calibrated for sine waves), ensuring reliable alternating voltage readings.

Current measurement includes both DC and AC: DC capability reaches up to 10 A, with ranges from 20 µA to 10 A and accuracies from ±1.2% (20 µA), ±1.0% (2 mA), ±1.5% (200 mA), and ±2.0% (10 A). AC current measurement offers similar flexibility and precision across 20 mA to 10 A with accuracy specs up to ±3.0% ±10 digits. A dual‑fuse design (200 mA and 10 A) protects the meter from overload.

Resistance measurement covers 200 Ω to 200 MΩ, offering resolutions between 0.1 Ω and 100 kΩ. Specified accuracy ranges from ±1.0% ±10 digits in low-ohm ranges to ±5.0% ±20 digits at 200 MΩ, making it suitable for continuity checks, circuit diagnostics, and component testing. Continuity mode triggers an audible buzzer when resistance falls below ~50 Ω, and diode testing applies a small test current for forward voltage verification.

Capacitance reading ranges from 2 nF to 200 µF, with resolution between 1 pF and 100 nF. Accuracy is specified as ±4.0% ±3 digits at low-cap ranges and ±5.0% ±3 digits at higher ranges. Frequency measurement extends to 200 kHz, with 100 Hz resolution and ±1.5% ±10 digits accuracy.

Temperature measurement, via an included Type‑K thermocouple, spans from –20 °C to 1000 °C, with resolution of 1 °C. Accuracy is ±5.0% ±5 digits below 0 °C, ±1.0% ±3 digits from 0 to 400 °C, and ±2.0% ±3 digits above 400 °C. Additional built-in functions include transistor hFE testing (range 0–1000 for NPN/PNP devices) and a remote IR signal detector—ideal for diagnosing electronic remote controls.

User experience is enhanced by features such as True RMS measurement, a large LCD display (~28 mm digits) with LCD backlight, auto-power-off, data hold, and a terminal shutter interlock mechanism to prevent incorrect lead insertion. A low battery indicator alerts users before power fades. The intuitive manual rotary switch simplifies mode selection, while the meter is protected from misuse via overvoltage safeguards.

Physically, the DM‑91 is compact and ergonomic, measuring 191 × 82 × 36 mm and weighing around 310 g (including battery). It includes all standard accessories—test probes, fuse, battery, Type‑K thermocouple probe, and user manual—making it immediately useful out of the box.

Safety-wise, the device conforms to IEC‑61010‑1 CAT II standards for working voltages up to 1000 V, and includes overvoltage protection across all ranges. It is engineered to be used safely in office, workshop, and residential environments, while the terminal shutter lock reduces risk of accidental contact.

In summary, the HTC DM‑91 Digital Multimeter is a compact powerhouse, combining broad-ranging measurement functions with precise accuracy, ergonomic design, and robust safety features. It is capable of measuring:

• DC voltage up to 1000 V with high precision

• AC voltage up to 700 V RMS, True RMS compliant

• DC/AC current up to 10 A, fused for protection

• Resistance up to 200 MΩ, including diode and continuity testing

• Capacitance and frequency measurements

• Temperature via thermocouple up to 1000 °C

• Transistor hFE and IR remote signal testing

Designed for field and workshop environments, its strong safety credentials, multifunction capability, and user-friendly design make it a reliable choice for technicians, electricians, educators, and hobbyists. Whether debugging circuits, verifying HVAC systems, or monitoring laboratories, this meter delivers consistent, trusted performance.