# HT Instruments HT21 Digital 4000-Count Multimeter # HT Instruments HT21 Digital 4000-Count Multimeter ## Key Features At A Glance - 3½-digit, 4000-count LCD with backlight, automatic polarity, and "OL" overrange indication - DC and AC voltage measurement to 600 V with 7.8 MΩ input impedance - Resistance from 400 Ω to 40 MΩ, plus diode and continuity testing (buzzer at R<150 Ω) - Capacitance measurement from 40 nF to 100 µF - Frequency measurement to 10 MHz and duty cycle from 0.5 to 99% - HOLD and REL functions with Auto Power-OFF after 30 minutes of idleness - Rated CAT III 600 V per IEC/EN 61010-1 with double insulation - Powered by a single 9 V battery (NEDA 1604 / IEC 6F22); 210 g including battery The HT21 is a handheld digital multimeter from HT Instruments (HT Italia SRL), built around a 3½-digit, 4000-point LCD that displays plus sign, decimal point, automatic polarity, and an "OL" overrange indication. A backlight supports reading in low-light conditions, and a low-battery symbol appears when the 9 V cell runs down. A digital multimeter consolidates the most common bench and field electrical measurements into a single instrument, reading voltage, resistance, and current-related parameters from a circuit or component. The HT21 integrates DC and AC voltage, resistance, diode, continuity, frequency, duty cycle, and capacitance functions, each available as an autoranging measurement so the operator does not need to select a range manually. ValueTronics stocks and holds its own inventory in a 20,000 sq ft secure warehouse at 1675 Cambridge Drive in Elgin, Illinois, so equipment is sourced and shipped directly from our own facility. ## Product Core & Specifications Specification Value DC Voltage (Autorange) — Accuracy ± (% reading + number of dgt) at 18°C ÷ 28°C, <70%HR; Input impedance: 7.8MΩ; Overload protection: 600VDC/ACrms 4.000V (Resolution 0.001V) ±(1.2%rdg+2dgt) 40.00V (Resolution 0.01V) ±(1.2%rdg+2dgt) 400.0V (Resolution 0.1V) ±(1.2%rdg+2dgt) 600V (Resolution 1V) ±(1.5%rdg+2dgt) AC Voltage (Autorange) — Accuracy (50 ÷ 400Hz); Input impedance: 7.8MΩ; Overload protection: 600VDC/ACrms 4.000V (Resolution 0.001V) ±(1.2%rdg+4dgt) 40.00V (Resolution 0.01V) ±(1.5%rdg+3dgt) 400.0V (Resolution 0.1V) ±(1.5%rdg+3dgt) 600V (Resolution 1V) ±(2.0%rdg+4dgt) Resistance (Autorange) — Overload protection: 250VDC/ACrms 400.0Ω (Resolution 0.1Ω) ±(1.2%rdg+4dgt) 4.000kΩ (Resolution 0.001kΩ) ±(1.0%rdg+2dgt) 40.00kΩ (Resolution 0.01kΩ) ±(1.2%rdg+2dgt) 400.0kΩ (Resolution 0.1kΩ) ±(1.2%rdg+2dgt) 4.000MΩ (Resolution 0.001MΩ) ±(1.2%rdg+2dgt) 40.00MΩ (Resolution 0.01MΩ) ±(2.0%rdg+3dgt) Diode Test — Overload protection: 250VDC/ACrms Resolution 1mV; Open voltage circa 1.5VDC ±(10%rdg+5dgt) Continuity Test — Overload protection: 250VDC/ACrms Buzzer R<150Ω Test current <0.3VmA Frequency (Autorange) — Sensitivity >8Vrms; Overload protection: 250VDC/ACrms 5.000Hz (Resolution 0.001Hz) ±(1.5%rdg+5dgt) 50.00Hz (Resolution 0.01Hz) ±(1.5%rdg+5dgt) 500.0Hz (Resolution 0.1Hz) ±(1.2%rdg+3dgt) 5.000kHz (Resolution 10Hz) ±(1.2%rdg+3dgt) 50.00kHz (Resolution 10Hz) ±(1.2%rdg+3dgt) 500.0kHz (Resolution 100Hz) ±(1.2%rdg+3dgt) 5.000MHz (Resolution 1kHz) ±(1.5%rdg+4dgt) 10.00MHz (Resolution 10kHz) ±(1.5%rdg+4dgt) Note: on AC Voltage the frequency range is 10Hz ÷ 10kHz; Sensitivity: > 15Vrms — Duty Cycle (Autorange) — Sensitivity >8Vrms; Overload protection: 250VDC/ACrms; 100µs < pulse duration < 100ms; Frequency range: 5Hz ÷ 150Hz 0.5 - 99% (Resolution 0.1%) ±(1.2%rdg + 2dgt) Capacitance (Autorange) — Overload protection: 250VDC/ACrms 40.00nF (Resolution 0.01nF) ±(5.0%rdg+7dgt) 400.0nF (Resolution 0.1nF) ±(3.0%rdg+5dgt) 4.000µF (Resolution 0.001µF) ±(3.0%rdg+5dgt) 40.00µF (Resolution 0.01µF) ±(3.0%rdg+5dgt) 100.0µF (Resolution 0.1µF) ±(5.0%rdg+5dgt) Display Type LCD, 3 ½ dgt, 4000 points plus sign and decimal point Polarity Automatic polarity indication Backlight Yes Overrange "OL" overrange indication Features Functions HOLD; REL; Auto Power OFF after 30 minutes of idleness Low battery indication Battery symbol appears when the battery voltage is low General Operating temperature 0°C to 50°C, <70%HR Storage temperature \-20°C to 60°C, <80%HR Max altitude 2000m Pollution degree 2 Insulation Double insulation Power supply 1x9V battery NEDA 1604 IEC 6F22 Battery life ca 30 h (backlight ON), ca 130 h (backlight OFF) Mechanical protection IP40 Size 138(L) x 68(W) x 37(H) mm Weight (included battery) 210g Applied standards (LVD) IEC/EN 61010-1 CAT III 600V Applied standards (EMC) EN60326 > **Important:** Rated CAT III 600 V per IEC/EN 61010-1 with double insulation. ## About this New unit This is a brand-new, factory-sealed unit, supplied exactly as it arrives from the manufacturer and backed by the full manufacturer warranty. For the exact configuration, available options, included accessories, or current lead time for your application, our Test Architects can confirm the details before you order. ValueTronics supplies both new and used test and measurement equipment. New units ship factory-sealed, exactly as received from the manufacturer; every used unit is inspected and functionally verified in-house at our 20,000 sq ft secure facility in Elgin, Illinois before it ships. Our Test Architects can help you select the condition, calibration, and configuration that fit your application. **Please review the Manufacturer's Data Sheet to verify published specifications. Feedback on this webpage is always welcome — please reach out to your Test Architect at any time for questions or concerns. Thank you, we truly appreciate you being our customer.** ## Details - **Price:** 95.0 USD - **Vendor:** HT Instruments - **Type:** Multi Met - **Tags:** HT Instruments, Manufacturers, Meters & DAQ, Multimeter, product_manual_group_3, Product_new ## Variants | Variant | Price | Available | |---------|-------|-----------| | Default Title | 95.00 USD | In stock | ## Images - HT Instruments HT21 Digital 4000-Count Multimeter --- > Source: [ValueTronics](https://valuetronics.com/products/ht21-ht-instruments-multimeter-new) > Updated: 2026-06-20