Typical applications for consumption measurement
A multimeter is an indispensable tool for most engineers and technicians when measuring current or voltage. However, when there is a need to measure the power consumption of a device, most multimeters often do not meet the necessary requirements: work at a high sampling rate, sufficient measuring ranges of current, or a quick data transfer to the PC for further analysis. Keysight Technologies’ 34465A/34470A multimeters provide, in addition to measurements of current, voltage, frequency, period, temperature, etc., measurement ranges of current and sampling rate ideal for consumption measurement.
Characterization of the power consumption of a battery powered device.
Design engineers are continuously working on optimising the power consumption of their devices, but for this they need accurate and reliable current measurements from idle to full activity to fully characterise current cycles. Typical working ranges for these applications range from mA to 10A, requiring a resolution of at least: microampere.
Testing the current consumption of a low leakage diode, or characterization of materials.
To test the current consumption of a low leakage diode, a pico-amp resolution with an upper limit of tens of mA is required. While these measurements can be made
(and power supply) with a higher-performance electro-meter, the most versatile and economical solution is to use a stable DC power supply and one of the new Truevolt multimeters from Keysight. These equipments have a low current range for measurements up to 1? A with a resolution of pA and a deviation of less than 100pA. Your
The upper current limit rises to 10A in both direct and alternating current.
Dynamic current measurements
Dynamic current measurements can be quite complex because a range change of the DMM is necessary based on the current level being measured. Keysight has specialized instruments (such as the SMU N6782A) that can simultaneously digitize power, voltage and current without range problems. While this may be a great solution for certain current characterization applications, the option of using a Truevolt multimeter is much more economical. A visual example: this figure describes the discharge of a battery, with a dynamic range of measurement automatically adjusted with the auto ranging function.
4 tips for performing these measurements
- When measuring very small currents, be sure to remove the previous readings from the display to increase the speed of automatic multimeter range change and to override possible offset configurations, and memory, so that it can be used during the entire measurement cycle (an alternative is simultaneous data dump to the PC).
- Consider positioning the multimeter in series with the power supply from the positive side. This way, if the voltage increases enough to exceed the DMM charging voltage (generated by the load flow through the multimeter’s internal resistance), you can supply the correct voltage to your device and measure the current with the highest accuracy of the multimeter.
- By using Keysight Multimeter Scanning Capability and the High Speed option, you can measure time-varying parameters with a time resolution of 20 µs. To scan efficiently with an accurate timing you must ensure that auto zero and auto ranging functions are disabled. This eliminates delays that are entered when the DMM makes additional readings for auto zero or switching to a different range.
- Use Keysight’s BenchVue software to remotely control and launch the measurements of two DMMs simultaneously. Also, use the DMM scanning mode to ensure 20 µS/sample synchronization between each equipment. Finally, note that the data logging mode via BenchVue on a PC includes by default the entry of header data that may slightly interfere with the measurement when extremely precise synchronization is required.