# BK Precision 388B Test Bench Digital Multimeter # BK Precision 388B Test Bench Digital Multimeter ## Key Features At A Glance - True RMS measurement for accurate readings on non-sinusoidal waveforms common in switching power supplies and variable-frequency drives - 20,000-count 4-1/2 digit LCD display with 0.05% DCV basic accuracy - DC voltage ranges from 200 mV to 1,000 V with 10 µV resolution; AC voltage to 750 V - Current measurement from 200 µA to 20 A with True RMS on all current ranges - Frequency measurement to 200 kHz and logic probe function with 20 MHz frequency response - Duty cycle measurement (0 to 90%) with 0.1% resolution across 40 Hz to 20 kHz - All current ranges fused with high-energy ceramic fuses; ruggedized dual-injection-molded case - Designed to meet IEC 61010-1 CAT III 1000V safety requirements with auto power off The BK Precision 391A is a True RMS handheld digital multimeter and the top-tier model in the Test Bench Series, a four-model family that also includes the 390A, 389A, and 388B. The 391A is positioned as the high-performance multifunction member of the family, combining a 20,000-count 4-1/2 digit LCD display, 0.05% basic DC voltage accuracy, and True RMS measurement on both voltage and current ranges. It is built into a ruggedized dual-injection-molded case designed to meet IEC 61010-1 CAT III 1000V safety classification, with all current ranges protected by high-energy ceramic fuses. Common applications across the Test Bench Series include resistance measurement, diode check, frequency measurement, and audible continuity — the everyday measurement tasks that bench and field professionals perform on electrical and electronic equipment. The 391A extends this baseline with logic probe and duty cycle measurement functions, making it suited to mixed analog and digital troubleshooting where standard multimeter functions alone would require swapping instruments. Manual ranging on the 391A gives the operator deliberate control over the measurement range, which is preferred in some diagnostic workflows over the auto-ranging behavior found on the 390A and 389A. ValueTronics International has supplied test and measurement equipment from its facility at 1675 Cambridge Drive in Elgin, Illinois since 1992, with all inventory stocked and {{CONDITION}} units tested in our 20,000 square foot secure warehouse. Equipment sold through ValueTronics is not drop-shipped from a third party — it passes through our own facility, where it is verified before shipment. For BK Precision Test Bench Series multimeters, this means the unit you receive has been physically handled and confirmed by our team rather than forwarded from an unverified source. ## Brand Heritage BK Precision is a long-established US-based test instrument brand specializing in general-purpose bench and handheld measurement equipment. The brand has operated continuously under the BK Precision name and is privately held with no significant corporate name changes affecting product continuity. ## Compare Other Models in This Series The Test Bench Series is a four-model True RMS handheld multimeter family from BK Precision: the 391A, 390A, 389A, and 388B. The four units share a common ruggedized dual-injection-molded case, CAT III 1000V safety design per IEC 61010-1, fused current ranges, and a core feature set covering resistance measurement, diode check, frequency measurement, and audible continuity. The family is differentiated by display resolution, DC voltage accuracy, ranging behavior (manual versus auto/manual), and the specific multifunction capabilities each model adds beyond the baseline. Within the family, the 391A is the top-tier model with 20,000-count 4-1/2 digit display and 0.05% DCV accuracy. The 390A and 389A are 4,000-count 3-3/4 digit auto/manual ranging instruments at 0.1% and 0.25% DCV accuracy respectively, with the 390A adding capacitance, temperature probe, relative mode, min/max hold, peak hold, and RS-232. The 388B is a 4,000-count manual-ranging model at 0.5% DCV accuracy that includes capacitance, transistor test (hFE), logic probe, and data hold. Each new model below is its own dedicated product page with condition-matched pricing and its own description of what is included. Use the comparison table to confirm the model best suited to the measurement task, then navigate to that model's listing for purchase details. The 391A's combination of 20,000-count resolution, 0.05% DCV accuracy, logic probe with 20 MHz response, and duty cycle measurement makes it the family member configured for users who need both higher display resolution and digital signal characterization from a single handheld instrument. The four Test Bench models trade off display resolution, DCV accuracy, ranging style, and supplemental functions. The 391A and 388B use manual ranging; the 390A and 389A use auto/manual ranging with a 41-segment analog bar graph. Capacitance measurement is present on the 390A, 389A, and 388B but not on the 391A. Temperature measurement is available only on the 390A (-58 °F to +2372 °F via thermocouple probe). Use the comparison table that follows to align the model to the specific measurement requirement. For high-resolution DC voltage work with logic probe and duty cycle, the 391A is the family configuration. For multifunction bench use with capacitance, temperature, and PC communications, the 390A is the configured option. The 389A and 388B serve lower-budget and component-test-focused requirements respectively. Model DCV Accuracy Display Count True RMS **388B** 0.5% 4000 (3-3/4 digit) No 391A 0.05% 20000 (4-1/2 digit) Yes 390A 0.1% 4000 (3-3/4 digit) Yes 389A 0.25% 4000 (3-3/4 digit) Yes Additional differences in specifications beyond the few shown above are not listed here — see each model's full specifications below. ## Accessories Supplied - 9 Volt Battery - Test Leads - Instruction Manual ## Product Core & Specifications Specification 388B True RMS No Ranging Manual Display 4000 count, 3-3/4 digit LCD Capacitance Measurement Yes Transistor Test Yes Logic Probe Yes Data Hold Yes DCV Ranges 400mV, 4V, 40V, 400V, 1000V ACV Ranges 400mV, 4V, 40V, 400V, 750V Voltage Resolution 100µV, 1mV, 10mV, 100mV, 1V DCV Accuracy ±(0.5% rdg + 1 dgt) ACV Accuracy ±(1.2% rdg + 4 dgt) 50Hz-500Hz; 750V: ±(2% rdg + 4 dgt); ±(1.5% rdg + 3 dgt) 500Hz-1kHz Voltage Overload Protection 1200VDC or AC rms; 500VDC/AC rms 15 sec on 200mV range Input Impedance 10MΩ Current Ranges 400µA, 4mA, 40mA, 400mA, 2A, 20A\* Current Resolution 100nA, 1µA, 10µA, 100µA, 1mA, 10mA DC Current Accuracy 400µA - 400mA: ±(1% rdg + 1 dgt); 2A: ±(1.5% rdg + 1 dgt); 20A: ±(3% rdg + 3 dgt) AC Current Accuracy 400µA - 400mA: ±(1.5% rdg + 1 dgt); 2A: ±(2% rdg + 4 dgt); 20A: ±(3.5% rdg + 4 dgt) Current Input Protection µA/mA: 2A/600V fast blow ceramic fuse; 20A: 20A/600V fast blow ceramic fuse Max Burden Voltage 600mV (900mV on 2A, 20A ranges) Resistance Ranges 400Ω, 4kΩ, 40kΩ, 400kΩ, 4MΩ, 40MΩ Resistance Resolution 100mΩ, 1Ω, 10Ω, 100Ω, 1kΩ, 10kΩ Resistance Accuracy 400Ω: ±(1% rdg + 4 dgt); 4kΩ to 4MΩ: ±(0.8% rdg + 4 dgt); 40MΩ: ±(2% rdg + 5 dgt) Open Circuit Voltage 0.6VDC typ. (3.2VDC on 400Ω range) Resistance Overload Protection 500VDC or AC rms Diode Test Tested at 1mA, 3.2VDC max. typ.; ±(1.5% rdg + 3 dgt) accuracy Transistor Test (hFE) hFE range: 0 - 1000; hFE base current: 10µA DC Capacitance Ranges 4nF, 40nF, 400nF, 4µF, 40µF Capacitance Resolution 0.1pF, 1pF, 10pF, 100pF, 1nF Capacitance Accuracy ±(3% rdg + 4 dgt) Test Voltage <3.5V Frequency Ranges 4kHz, 40kHz, 400kHz, 4MHz Frequency Resolution 1Hz, 10Hz, 100Hz, 10kHz Frequency Accuracy ±(0.1% + 2 Digits) Frequency Sensitivity 250mVrms min. on 10Hz to 1MHz; 500mVrms min. on 1MHz to 4MHz Minimum Pulse Width \>2µs Logic Threshold Hi=2.8±0.8V, 0=0.8±0.5V Logic Frequency Response 20MHz Logic Pulse Width 25ns Logic Pulse Limits \>20% and <80% Logic Indication 40msec beep at logic 1 (Hi) Logic Overload Protection 500V DC or AC rms Safety Designed to meet IEC61010-1 CAT III 1000V, class 2 \* 20A range 10A continuous, 20A for 30 seconds max. **Important:** All current ranges are fused with high-energy ceramic fuses. The 20 A range is rated for 10 A continuous and 20 A for 30 seconds maximum.**Important:** 20A current range is rated for 10A continuous; 20A is permitted for 30 seconds maximum.**Important:** Thermocouple Probe is supplied with the Model 390A only; the 391A, 389A, and 388B do not include a temperature probe in standard delivery.**Important:** Carrying Case (LC-29B) is not included with the multimeter and must be ordered separately. **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:** 175.0 USD - **Vendor:** BK Precision - **Type:** Multimeter - **Tags:** BK Precision, Manufacturers, Meters & DAQ, Multimeter, product_manual_group_1, Product_new ## Variants | Variant | Price | Available | |---------|-------|-----------| | Default Title | 175.00 USD | In stock | ## Images - 388B BK Precision Multimeter --- > Source: [ValueTronics](https://valuetronics.com/products/388b-b-k-precision-multimeter-new) > Updated: 2026-05-30