Why is the Maximum Allowable Common Mode Voltage Lower for Direct Input Cables in the DL850 Isolation Modules?

 The isolation module specifications for maximum allowable common mode voltage using direct input is 42V(DC+ACpeak).

The maximum allowable common mode voltage using the 701901(1:1) safety cable is 400V or more. 
The specification written as "Direct input or cable not complying with the safety standard can be interpreted as directly inputting a cable, which is not complying with the safety standard, to the BNC input of the DL850 isolation modules. The 42V specification is not a limitation of the module, but it is a human safety limitation to prevent harm to the user.
A metallic connector is an example of direct input, which is not complying with the safety standard, or a cable which is not complying with the safety standard. A metallic connecter connected to the isolated input module can potentially induce a high voltage on the metallic connecter.
Therefore the maximum common mode voltage must be less than the voltage by which we are injured from electric shock.

Related Products & Solutions

Data Acquisition (DAQ)

Data acquisition (DAQ) is the measurement, recording, analyzing, and presentation of real world phenomena. It includes electrical measurements such as voltage, current, power as well as measurements through sensors and transducers including temperature, pressure, strain, vibration, and more.

High Speed Data Acquisition

Yokogawa high speed data acquisition systems deliver industry leading isolation, bit resolution, sampling rate, and memory depth, with independent channel hardware and easy to use software.


Capture, analyze, and troubleshoot electrical or real-world physical signals. Oscilloscopes observe the change of electrical signals over time, continuously graphed on a display as voltage or amplitude vs. time.


A ScopeCorder is an instrument combining a mixed signal oscilloscope and portable data acquisition recorder into a modular platform designed to capture both high-speed transients and low-speed trends. Yokogawa’s ScopeCorder product family provides flexible and high-performance multi-channel test instruments by combining a variety of signal conditioning input modules, onboard calculations, and deep data acquisition storage into an off-the-shelf data acquisition solution.