# B&K Precision 391B True RMS Handheld Digital Multimeter # B&K Precision 391B True RMS Handheld Digital Multimeter ## Key Features At A Glance - CAT III 1000 V / CAT IV 600 V safety rating for distribution-panel and service-entrance work - True RMS AC and AC+DC measurement across voltage and current functions - Display counts from 40,000 (390B/391B) to 100,000 (393B) with dual display and analog-style bar graph - DC voltage basic accuracy from 0.03% (390B/391B) down to 0.015% (393B) - Measurement functions include DCV, ACV, AC+DC, DCI, ACI, resistance, capacitance, frequency, diode, temperature, and continuity test - Optical isolated USB interface on all models for PC data logging; Bluetooth wireless logging on Model 390B only - Internal data logging capacity of 40,000 readings (390B) or 20,000 readings (391B/393B) - Dirt and water-resistant housing with rubberized protective case for field use The BK Precision 390B Series is a family of three True RMS handheld digital multimeters — the 390B, 391B, and 393B — designed for general purpose measurement applications across electronics and electrical systems. Each model in the series combines True RMS AC and AC+DC measurement capability with a dual-line display, analog-style bar graph, and a comprehensive set of measurement functions including DCV, ACV, AC+DC, DCI, ACI, resistance, capacitance, frequency, diode, temperature, and continuity test. The series is bundled with a complete set of accessories and is intended for technicians and engineers who need accurate results, data logging, and field-ready measurement features in one instrument. A handheld digital multimeter is the universal diagnostic instrument of the electrical and electronics professional — measuring the three fundamental electrical quantities of voltage, current, and resistance, along with secondary parameters such as capacitance, frequency, and temperature. The 390B Series is built for the working technician or engineer who needs a single instrument that handles general-purpose bench work, field service, and industrial maintenance. The True RMS architecture ensures accurate measurement of non-sinusoidal AC waveforms — the kind produced by variable-frequency drives, switching power supplies, and LED lighting loads — where average-responding meters would report incorrect values. ## Compare Other Models in This Series The 390B Series is a three-model family of True RMS handheld digital multimeters from BK Precision. All three models share the same overall measurement function set, the same CAT III 1000 V / CAT IV 600 V safety rating, the same physical form factor, the same protective case and accessory bundle, and the same 3-year warranty. The differences between the three are concentrated in three specific dimensions: display resolution, DC voltage basic accuracy, and connectivity options. Within the series, the 390B is the wireless-enabled variant with Bluetooth connectivity and the largest internal data log capacity. The 391B is the wired-only variant with the same 40,000-count display and 0.03% basic DC accuracy as the 390B. The 393B is the precision variant, stepping up to a 100,000-count display and 0.015% basic DC voltage accuracy. Each model serves a specific use case within the same overall application space. Each model in the 390B Series is listed on its own dedicated product page with new-matched pricing and inventory. Use the comparison table below as a quick orientation across the three; click through to the specific model that matches your application for full specifications, current pricing, and ordering. The clearest differentiator across the series is the connectivity choice. The 390B is the only model in the family with Bluetooth wireless connectivity, supporting the B&K Precision Link mobile app for live measurement monitoring from an Android or iOS device. The 390B also has the largest data log capacity at 40,000 readings versus 20,000 readings on the 391B and 393B. The 390B is also the only model with AutoV/LoZ automatic AC/DC voltage detection. The second clear differentiator is display resolution and DC accuracy. The 390B and 391B share a 40,000-count display, while the 393B steps up to a 100,000-count display. Basic DC voltage accuracy follows the same pattern: 0.03% on the 390B and 391B, improving to 0.015% on the 393B. The 391B and 393B both add duty cycle measurement, which is not available on the 390B. Model Display Count DCV Basic Accuracy Wireless Data Logging **391B** 40,000 count 0.03% No 390B 40,000 count 0.03% Yes 393B 100,000 count 0.015% No Additional differences in specifications beyond the few shown above are not listed here — see each model's full specifications below. ## Accessories Supplied - Test leads - K-type thermocouple adapter - Protective case - Optical-isolated USB cable - Magnetic hanging kit - Alkaline batteries ## Product Core & Specifications Specification 391B Display 4,000 / 40,000 count DCV Basic Accuracy ± (0.03% + 20 digits) AutoV/LoZ No Wireless Data Logging No Measurement Speed 3 times per second Data Log Capacity 20,000 measurements Connectivity IR-USB Duty Cycle Yes Temperature Probe Yes DC Voltage Ranges 40.000 mV / 400.00 mV / 4.000 V / 40.000 V / 400.00 V / 1000.0 V DC Current Ranges 40.000 mA / 400.00 mA / 4.0000 A / 10.000 A Resistance Ranges 400.00 Ω to 40.000 MΩ Capacitance Ranges 4.0000 nF to 40.000 mF Frequency Ranges 40.000 Hz to 100.00 kHz Temperature Range \-200 °C to 1200 °C (-328 °F to 2192 °F) Continuity 400.00 Ω, 0.2 + 30 Diode Test 2.0000 V, 1.5 + 20 Power 4 x 1.5 V AA size batteries Battery Life (typical) 100 hours Auto Power Off Adjustable up to 30 minutes or never Operating Temperature 14 °F to 122 °F (-10 °C to 50 °C) at ≤ 80% RH Storage Temperature \-4 °F to 140 °F (-20 °C to 60 °C) Safety EN61010-1 to 600 V CAT IV / 1000 V CAT III Electromagnetic Compatibility EMC Directive 2014/30/EU, EN61326-1:2013 Dimensions (W x H x D), without case 3.8" x 8.2" x 2" (95 mm x 207 mm x 52 mm) Weight 1.4 lbs (630 g) Warranty 3 Years **Important:** Maximum continuous current measurement time: 10 minutes at mA inputs, 1 minute at A inputs, with a 20-minute minimum rest time after continuous measuring.**Important:** AutoV/LoZ and Bluetooth wireless data logging are available on Model 390B only.**Important:** Max. Continuous Measuring Time: 10 minutes at mA inputs, 1 minute at A inputs. Min. Rest Time: 20 minutes after continuous measuring.**Important:** Overload Protection: AC/DC 1000 V for voltage; AC/DC 400 mA at mA inputs, AC/DC 10 A at A inputs for current.**Important:** Temperature specification does not include error of the thermocouple probe; specified after 60 minutes of warm-up time.**Important:** Accuracy specifications apply at 23 °C ± 5 °C with relative humidity less than 80% RH, on a one year calibration cycle. **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:** 488.0 USD - **Vendor:** B&K Precision - **Type:** Multimeter - **Tags:** BK Precision, Manufacturers, Meters & DAQ, Multimeter, product_manual_group_3, Product_new ## Variants | Variant | Price | Available | |---------|-------|-----------| | Default Title | 488.00 USD | In stock | ## Images - B&K Precision 391B True RMS Handheld Digital Multimeter --- > Source: [ValueTronics](https://valuetronics.com/products/391b-b-k-precision-multimeter-new) > Updated: 2026-05-30