Digital multimeter with insulation resistance measurement BM878 TRMS VFD, T, Riso 50V-1000V Earth Cont. 200mA 102133

Comprehensive Installation Diagnostics in a Single Device

Replacing a traditional multimeter with a multifunctional device capable not only of measuring voltage but also of checking insulation integrity and grounding continuity is a step toward significantly faster and safer work. The BM878 model combines the functions of a precise True RMS multimeter, a professional insulation tester, and a grounding circuit analyzer. This enables installers and service technicians to perform full preventive diagnostics without carrying three separate instruments. The device supports measurements in safety categories CAT III 1000V and CAT IV 600V, making it suitable for work in main distribution boards and at low-voltage connections.

Applications and Key Measurement Functions

The main advantage of this model is its ability to test insulation resistance at five different voltage levels: 50V, 100V, 250V, 500V, and 1000V. This allows precise adaptation of test conditions to the type of cable or device under test—from delicate electronics to heavy industrial installations. The maximum measurement range reaches an impressive 25 GΩ, enabling detection of even subtle insulation defects before they lead to failure. For continuity checks of protective and equipotential bonding circuits, the meter generates a test current of 200 mA. Such a high current can penetrate layers of rust or contamination on contacts, ensuring reliable results where standard multimeters (with currents in the range of a few mA) might incorrectly indicate an "open circuit".

The device is equipped with advanced low-pass filters (LPF), which are crucial when working with variable frequency drives (VFDs). Thanks to these, AC voltage and frequency measurements remain accurate even in environments with significant harmonic disturbances. The meter supports ranges up to 600 V AC (True RMS) and 1000 V DC, and also measures current up to 600 mA, capacitance up to 30 mF, and temperature in the range from -50°C to 537°C. Fast result sampling—up to 4 times per second on the main display and 40 times per second on the bargraph—allows easy tracking of value changes in real time, which is invaluable when searching for short circuits or unstable connections.

User Safety and Work Ergonomics

Safety during measurements is ensured by the Beep-Jack™ system. This feature acoustically warns the user against attempting to connect a probe to an incorrect input jack, drastically reducing the risk of device damage or electric shock when measuring voltage with test leads connected in resistance mode. Additionally, measurement lockout in live circuits prevents accidental initiation of insulation tests where it would be hazardous.

Ease of operation is enhanced by a large backlit LCD display and a Hold function to freeze results. For long-duration tests, a LOCK-TEST mode is available, while the SMOOTH mode smooths out readings during insulation resistance measurements, eliminating value fluctuations caused by electrical noise. The ZERO function allows compensation for the internal resistance of test leads, which is essential for precise low-resistance measurements.