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HEWLETT- PACKARD
JOURNAL
T E C H N I C A L I N F O R M A T I O N F R O M T H E - h p - L A B O R A T O R I E S
Vol. 11, No. 11-12
JBLISHED BY THE HEWLETT-PACKARD COMPANY, 1501 PAGE MILL ROAD, PALO ALTO, CALIFORNIA JULY- AUG., 1960
A New Clip-On Oscilloscope/Voltmeter Probe
For 25^-20 MC Current Measurements
TWO years ago -hp- introduced a dc milliammeter can be used equally well with pulse and other com
that used a clip-on probe to couple to the conduc plex waveforms as with sine waves. Further, because
tor that carried the current to be measured. Because it has the outstanding property of reflecting virtually
it merely clipped around the conductor and thus no loading into the circuit being measured, the probe
avoided the need for breaking the circuit, this probe enables current to be measured with ease in cases that
changed the measurement of current from an incon previously would have been considered impractically
venient and sometimes difficult measurement to an difficult. Such cases include measuring the current in
easy measurement. Later, this dc instrument was fol circuits at resonance, in ground buses, in solid-state
lowed by another clip-on probe type instrument rectifiers at turn-on, etc.
which measured ac current in combination with the The probe operates with an accompanying small
-hp- wide-band oscilloscope. amplifier (Fig. 3) to convert the ac current being
The popularity of these clip-on probes for current measured to a proportional voltage. This voltage can
measurements has now led to the development of a then be measured with a suitable oscilloscope or volt
new and even more flexible clip-on probe