Specifications

A passive probe and its accessories

Let's look at a typical passive probe. The following picture shows a B&K Precision PR37AG 150 MHz

1X/10X switchable probe and its 15 cm ground clip that ends in an alligator clip (the scale is graduated

in mm):

Figure 37

The orange switch has positions X1, X10, and REF. The REF position grounds the center conductor

and disconnects the input, allowing you to see the position of 0 volts on the oscilloscope's screen.

Note the tip is a sharp point and that a band of metal is a few mm behind the tip (the probe comes with

one replacement tip). This metal band is connected to the probe's ground and is used to ground high

frequency measurements. The left end of the grounding lead plugs into the probe about 1 cm to the

right of the orange switch (i.e., just to the right of the finger guard) and clips in place.

Using this probe as shown is not recommended, as it's too easy to accidentally short a conductor with

the grounded band of metal. Instead, accessories such as the following are placed over the tip:

Figure 38

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