7½-digit DMM has 1 MHz sampling, plus graphical display

January 22, 2015 // By Graham Prophet
Termed by Keithley the first “graphical sampling digital multimeter” the DMM7510 combines high accuracy, integrated data visualisation, and operation via a capacitive touch screen with an interface that is modelled on the “smartphone experience”

The DMM integrates a high accuracy digital multimeter, a digitiser for waveform capture, and a capacitive touchscreen user interface. Its user interface is a development of that which is already offerd on some of the company’s “Touch, Test, Invent” Source-Measure units.

Keithley says that the design philosophy of the instrument is based on helping engineers to get an in-depth understanding of their devices under test, in a context where they need to capture small signals at higher accuracy and faster speeds than traditional DMMs can provide. The Model DMM7510 uses an 18-bit conversion, with a peak sampling rate of 1 Msample/sec. Basic accuracy is 14 ppm (parts-per-million). It can display a graphical representation of the captured samples, but Keithley is careful to point out that this is not updated as is a scope display.

You operate the instrument with a graphical touchscreen which responds to a range of gestures (swipe, etc.) that are borrowed from smartphone and tablet computer practice (or by means of conventional rotary-knob control), and there is internal processing to carry out analysis of the captured data points; “You don’t need a PC to analyse the data”, Keithley says. The instrument can be set to capture data points following trigger events; trigger types are in the analogue domain (that is, they scale to the range the DMM is measuring) and include edge, pulse and window conditions.

Resolution level are selectable from 3½ to 7½ digits; the unit provides DC accuracies “typically only found in metrology-grade instrumentation—but at about half the price of those solutions” the company asserts. The 14ppm basic 1-year accuracy applies to DC voltage measurements. Expanded measurement ranges (100 mV, 1Ω, and 10 µA) enhance low level accuracy. On the 10 µA range, resolution is therefore 1 pA: at the other end of the scale, the 7510 has a 10A current range, without use of external shunts. An auto-calibration feature minimises temperature and time drift.