Floating Oscilloscope Measurements ... And Operator Protection

• Isolated-input Oscilloscopes
• Conclusion

Isolated-input Oscilloscopes

Figure 9. - THS720P TekScope Isolated Channel oscilloscope.

Figure 10. - P5102 High Voltage Probe for the THS700 Series.

Isolated-input oscilloscopes such as the Tektronix THS700 Series (THS710A, 60 MHz; THS720A, 100 MHz; THS730A, 200 MHz; THS720P, 100 MHz - see Figure 9) are hand-held, battery operated oscilloscopes that feature dual input channels, individually isolated from the oscilloscope's chassis as well as from each other. This allows dual-trace waveform comparisons to be made, with each of the two channels referenced to its own common. The safe operating voltage of these oscilloscopes depends on the probes used.

The standard 10X P6117 probe is rated for IEC category II applications up to 300 V_RMS tip-to-common, with the common lead floating up to 30 V_RMS above earth ground. This range is suitable for most typical measurements on low-voltage electronics circuits.

For higher voltage applications, the THS710A, THS720A, THS720P, and THS730A, with the 10X P5102 Probe (see Figure 10), are rated for IEC category II applications up to 1,000 V_RMS tip-to-common, with the common lead floating up to 600 V_RMS above earth ground. This combination of scope and probe takes full advantage of the THS700 Series IsolatedChannel^TM architecture and allows safe probing of floating signals, providing protection to both the user and the equipment under test.

Conclusion

Tektronix has reviewed these methods in an effort to increase user awareness regarding the potential dangers inherent in the improper operation of oscilloscopes.

Our commitment to Test and Measurement Product Safety has resulted in the isolated input oscilloscope, isolation amplifiers, and differential products described here. If you feel your applications would be more safely and accurately served by these products, please contact your nearest Tektronix representative.

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