Technical Insights > Benchtop

Digitizing Measurements with a DMM Isn't a Dream

2019-08-14  |  5 min read 

Multimeters of the past were analog with an analog needle pointing to a measurement scale on a meter dial. Such analog multimeters cannot detect fast changes from your measurement signals. Analog multimeters can only measure a signal at a steady-state or a stable measurement condition. Some modern digital multimeters now have an analog to digital converter circuits that can sample your signals, capture them into a fast memory buffer, and displayed in an informative graph on a large screen. This new feature is known as a digitizing acquisition mode.

What is the difference between digitizing and normal acquisition mode?

Typically, in a normal acquisition mode for a DMM, measurements are taken continuously and reside in a temporary first in first out (FIFO) buffer. Measurements in this mode display live in digits or in a simulated analog bar scale.

You can set the sampling rate and the duration time of the measurement window in a digitizing acquisition mode. The sampling rate and duration time have limitations depending on the DMM’s hardware capabilities. A DMM sampling rate typically is within the kHz to MHz range. In comparison, an oscilloscope or a dedicated digitizer sampling rate is from the MHz to GHz range. The duration time has limitations because of the memory available in the hardware. Some DMMs extend its memory by allowing storage of captured signals into a USB thumb drive.

Digitizing is the process of converting a continuous analog signal into a series of discrete samples or readings (Figure1) to give you additional insights into the signal’s characteristics.

A sampling of an analog signal
Figure 1. A sampling of an analog signal

The digitized signal is either uploaded to a remote device such as a PC or displayed as a trend chart (Figure 2) on the display of a DMM. The trend chart capability of the DMM complements the digitizing process by providing a graphic representation of the data over time.

Trend chart of a digitized signal
Figure 2. A trend chart of a digitized signal captured by a DMM

What can you do with a DMM’s digitizing acquisition mode?

DMMs are always a versatile tool for measuring various types of signals. When DMMs have a built-in digitizer and triggering capability, it can measure transient signals.

A DMM with a digitizer can help you:

  • Troubleshoot a fault condition of a high voltage power source
  • Evaluate the current consumption of a portable device (Figure 3)
  • Characterize a sensor’s step response time

Current consumption display on DMM
Figure 3. Current consumption measurements of a portable device using a DMM

The display of a versatile DMM allows you to zoom in and out of your signal, pan your captured signal, and even apply X (horizontal) and Y (vertical) cursor markers to register accurate measurement to the exact signal location of interest.

A DMM’s digitizer may not have a very high sample rate or input bandwidth like an oscilloscope or a dedicated digitizer. However, it is sufficient to cover many low-frequency application measurements.

Summary

The digitizing and advanced triggering capabilities are a standard feature when you buy any of Keysight’s Truevolt DMMs — such as the 34465A and 34470A.

Use Table 1 to help you select the right Truevolt DMM for your applications.

Key Specification

34465A

34470A

Digits of resolution

6 1/2

7 1/2

Max reading rate

50000 readings/second

50000 readings/ second

Memory

2 million readings

2 million readings

Bandwidth

   

DCV (all ranges)

15 kHz

15 kHz

DCI (all ranges)

10 kHz

10 kHz

Table 1. Key specifications for Keysight’s DMMs for digitizing applications

Models 34465A and 34470A come with the advanced triggering capability to complement the digitizing acquisition function. They also come with graphical front panel display with the built-in trend, histogram, math, and statistical tools for real-time analysis.

For more information on Keysight’s Truevolt DMMs, please visit our website at www.keysight.com/find/truevolt.

To learn more, read 10 Things You Must Know Before Buying Your Next Benchtop Digital Multimeter.