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NI DMM Error -1074118625: Volt-Hz Common Mode Limit

Hardware: Modular Instruments>>Digital Multimeters (DMM)

Problem:
I am using an NI DMM, and occassionally run into the following error:

 "Error -1074118625: niDMM Read Waveform (waveform data).vi. The Volt-Hz common mode limit has been exceeded."

What does this error mean, and what can I do to remedy it?

Solution:
To immediately remedy this error, you can reset the DMM to restore it to a functional state.  You can either do this in the Measurement and Automation Explorer (MAX) by finding the DMM in Devices and Interfaces and resetting it there, or programmatically by using the niDMM Reset function or VI

The error mentioning that the Volt-Hz limit had been exceeded usually occurs when the DMM encounters a high frequency power spike. That is, a high voltage signal of high frequency content (i.e. a glitch) is being applied to the DMM. This is a fairly common occurrence if you are switching high voltages and there is debouncing.

In theory, when there are such powerful transients being routed through the DMM, these transient signals cause a lot of electromagnetic noise that actually disrupt the digital communication between the daughter card and the mother card (where the digitized information is sent to the PC). When the DMM enters such a state where the communication has been disrupted, you must reset the device in MAX in order for it to operate properly again.

The Volt-Hz limit is specified in the specifications for each DMM. For example, page 6 of the NI 4070 specifications states the maximum Volt-Hertz product is 8 × 10⁷ V-Hz.

The user can recover from this state once the error occurs by calling the following series of VIs or(functions):

niDMM Reset (niDMM_reset)

Any configuration VI or function to reconfigure the instrument to the required settings

niDMM Initiate (niDMM_Initiate), niDMM Read (niDMM_Read), or niDMM Read Multipoint (niDMM_ReadMultipoint) to restart the measurement

If your application includes switching high voltages, you can remove these transient power spikes by including a low-pass RC filter before the signal is sent to the DMM.

Related Links:
NI 4070/4072 Specifications (February 2007)


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Report Date: 02/05/2007
Last Updated: 01/23/2008
Document ID: 464E7HJQ

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