Which connection cables to choose for HIOKI SW100x multiplexers?

Suppose you need to test the quality of the contacts - the welded joints of Li-ion battery modules. At the same time, you are in a situation where one of the key requirements for testing is speed, because you are performing this test in a production environment. One way to make this measurement in the shortest possible time would be to purchase as many HIOKI RM3545 resistance meters as you have total connections to test on each battery module, and make all these measurements in parallel. Well, you probably recognize that this is probably not the right thing to do, at least in terms of the initial investment in instrumentation.

HIOKI therefore also offers multiplex solutions such as the SW1001 or its bigger brother SW1002. With a channel switching speed of just 11 ms/k., these switching units allow you to perform the above weld contact checks almost as fast as parallel testing. In addition to lower costs, this solution is also much easier in terms of integration into your production environment than deploying multiple measuring instruments in parallel.

HIOKI SW1001 Switch Mainframe
Figure 1: HIOKI SW1001 Multiplexer

Of course, the SW100x series switching units are not only for resistance measurements, but also for voltage measurements and general Li-ion battery testing (detailed below - using the BT4560). Depending on the specific application and the measuring instrument, the measurement principles vary slightly; they are either 2-wire, 4-wire or 4-terminal pair measurements.

The most common example for two-wire measurements are voltage measurements using a digital voltmeter such as the HIOKI DM7276. The voltmeter in this case will be connected to terminal 1 of the switching unit, with the optional input module for connection from the DUT side being the one labeled SW9001 (the module on the left side of Figure 2).

Instruments connect to terminals 1, 2 and 3.jpeg
Figure 2: Measuring instruments are connected to terminals 1, 2 and 3

Four-wire measurements are typically resistance measurements with the aforementioned RM3545 or battery/battery cell tests with a 1kHz-ACIR battery tester such as the now de-facto industry standard BT3562A, also from HIOKI. Here the instrument would be connected to terminal 2 and the input module would again be SW9001.

The multiple DUTs are connected to multiplexer modules SW9001 or SW9002.jpeg
Figure 3: DUTs are connected to the input modules SW9001 or SW9002

Finally, applications with 4-terminal paired measurement require six wires instead of four, because two additional wires are needed for reverse current, which helps minimize the effects of eddy currents. The instrument in this case is the HIOKI BT4560 (Battery Impedance Meter). This instrument connects to the switching unit at terminal 3 and requires an input module labeled SW9002. By the way, if you are asking why coaxial cables - their shielding is used just to transmit return currents.

Anyway, back to the connection between the DUT and the SW100x series switching units just introduced: all of the above means one thing in the end, namely that there is simply no single "one-size-fits-all" cable. In addition to the number of conductors in a given connection, the length and the way in which these cables are routed also influence the measurement results, as each task requires a specific approach. This is why these cables are not offered by HIOKI and instead are usually custom-made only by system integrators according to the exact requirements of the specific application (and customer).

The user manual for the SW100x switching units specifies the technical requirements for the cables that can be used in terms of maximum capacitance and resistance, but no longer specifies cable types or specific models. One reason for this is that cables commonly used in Asia may not be as common in Europe. However, this naturally leads to questions from customers about recommendations for suitable cables and connectors.

If you are planning to use SW1001 or SW1002 for two- or four-wire measurements with SW9001 modules, a suitable cable available in Europe is a cable from Lapp Group called UNITRONIC LiHCH (TP) 25x2x0.14 (item number 0038325). This is a version of the cable with 25 twisted pairs of cables. However, if you need fewer pairs or would prefer to split the bundle, you can of course choose other versions of this cable. The cable is available in the required lengths from the LAPP online shop.

As a connector, you can use any D-sub female connector type DD-50, for example from HARTING Technology Group (item number 09 67 050 4704), which is available from Farnell Electronics (order number 2752194).

Cable and connector recommended for SW9001.jpeg
Figure 4: Recommended cable and connector for SW9001

If you plan to use the SW100x for 4-terminal paired measurement applications (e.g. with the HIOKI BT4560 battery impedance meter and SW9002 modules), a suitable cable is the "RG 174 UR" from Caledonian Cables. But beware of one small detail - there is a big difference in the resistance of the "normal" RG 174 cable and the required RG 174 UR cable. The former, which can be found almost everywhere, does not meet the requirements for use with the SW9002.

As a connector you can use any D-sub female connector type DC-37, for example from Harting (item number 09 67 037 4704), which is also available from Farnell Electronics (order number 1096857).

After selecting the right cables and connectors, the next step is to arrange them correctly with respect to maximum length and also to eliminate other influences such as eddy currents. But that's another story...

Thanks to my colleagues Elmar Schildbach, Makoto Takizawa and Yuto Akamatsu for their market research and testing of possible solutions. However, a small disclaimer at the end: the compilation of the information on the proposed third-party products has been done with the utmost care, yet no guarantee is hereby given for correct implementation in a specific application. Therefore, the procedures suggested in this article are only recommended and the guarantee of accurate and safe measurements remains the responsibility of the system integrator.


Kai Scharrmann, HIOKI EUROPE GmbH