RM3546 Resistance Meter

• max. measuring current 1 A
• 6 1/2 digit display
• fully automated data logging
• measurement speed up to 2.3 ms per sample
• comparison function, temperature compensation, self-calibration, etc.
• RS-232C, USB, LAN, EXT I/O as standard
• the instrument allows direct saving of the measured value to Excel or a text editor by pressing the Enter button on the front panel (via USB cable)

*Advanced Temperature Compensation (A-TC) function

After welding, the electrical resistance of the joint changes with the temperature during the cooling phase, which can complicate the evaluation of the measurement results, even if the quality of the weld itself remains unchanged. In practice, this requires either waiting for complete cooling before measurement or including the temperature at the weld site in the resistance evaluation, which in turn requires a reliable and reproducible reference regarding the temperature at the time of measurement.

To reduce such temperature deviations, the RM3546 uses advanced temperature compensation (A-TC). Resistance values are compensated using an external, temperature-coupled process signal that represents the temperature conditions at the time of measurement. The RM3546 accepts an analog input signal in the 0 to 2 V range, which is the commonly used format for representing temperature values from suitable infrared thermometers or process sensors. The AT-C thus supports more consistent evaluation of resistance measurements, including measurements taken shortly after the welding process:

Detailed product overview

The RM3546 is a DC resistance meter optimized for checking the resistance of welds on battery cells and modules. It supports stable measurements in microohms made shortly after welding, when the joint is still cooling and resistance values are affected by temperature changes, extended wiring and multiple contact interfaces along the measurement path. The instrument also includes active circuit protection up to 60 VDC for safe manual resistance measurements during battery module service.

Introduction of the RM3546 - video:

Practical demonstration of electrical resistance measurement of a weld joint - video:

The RM3546 offers 13 resistance ranges from 1 mΩ to 1000 MΩ with a maximum test current of 1 A. The lowest 1 mΩ range provides the resolution needed to accurately evaluate even minimal resistance changes in welded joints, with measurement resolution down to 1 nΩ and a basic accuracy of ±0.045% rdg ±0.010% f.s. Optional internal Z3003 switching cards allow automated multi-channel resistance measurements without the need for an external scanner or additional control hardware.

Measurement integrity

For even greater reliability and stability of low resistance measurements under thermally and electrically variable conditions, the RM3546 offers Advanced Offset Voltage Compensation (A-OVC) and thermoelectric power. By applying test current in both directions and averaging the results, these effects are minimized. In addition, resistance changes associated with temperature increases are evaluated and insufficient probe contact is detected, helping to reduce measurement errors caused by temperature effects or poor electrical connections.

Measurement automation and system integration

For automation and data acquisition, the RM3546 offers LAN, USB, and RS-232C interfaces for communication with PCs and controllers, as well as an EXT I/O interface for external triggering and PASS/FAIL signaling of measurement results. An analog D/A output (0 V to 1.5 V DC) is available for monitoring or feedback. During system setup and commissioning, the command monitoring function displays communication commands and responses directly on the instrument, supporting efficient debugging and reducing integration requirements.

Expandability for multi-position measurements

Up to two optional Z3003 switching cards can be installed in the RM3546 instrument body, each providing 10 channels for measurement in four-wire mode (21 in two-wire mode). When two cards are installed, the instrument can automatically measure up to 20 (or 42) channels (in sequence), allowing the resistance of multiple devices under test to be evaluated without manual rewiring. Installation of the cards into the instrument requires only a Phillips screwdriver and takes approximately two minutes.

For applications requiring more than 20 channels, the RM3546 can alternatively be combined with the HIOKI SW1002 multiplexer system, which offers up to 132 channels in four-wire mode.

Battery contact measurement during service

In service applications, the measurement of battery contact resistance and bonding is usually performed manually using conventional measuring cables. Thus, during manual measurement, one end of the probe may come into contact with the live bus, while the other end may touch the chassis or other grounded part of the equipment/rack by careless handling. Without a suitable protective feature, such situations can lead to damage to the instrument.

For this reason, the RM3546 is equipped with Active Circuit Protection (ACP) up to 60 VDC. This feature protects the instrument from inadvertently applying voltage to the measurement input and facilitates safe use in a service environment. Although Active Circuit Protection is primarily relevant for service applications, it also provides an additional level of protection during system setup, commissioning or maintenance in a production environment.