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Scope probes are much much more than “bits of wire”. They are surprisingly sophisticated pieces of technology containing very thin wires and precision components:

  • fragile and easily damaged: a damaged probe is as useful as a chocolate teapot - and can easily waste a day of your (remaining) life
    • do not kink, twist, stretch, or coil the leads, or, as you often see in EBay listings, put a rubber band around them!
    • do not use on high voltages, where high is >20V at some frequencies
    • don't lose the accessories such as grabbers and ground spikes - they are vital to the correct operation of the probe
  • expensive: when buying a second-hand scope the rule-of-thumb is to spend more on the probes than on the scope. The Agilent probes cost £130+VAT each, and they are relatively low-cost for a decent probe. Many probes cost >£700, Farnell sells a probe costing £5,500, and some probes cost much more than that
  • vital: your measurements will only be as good as your scope probes and the accessories

Use the right probe for your job:

  • safety don't use any of the HackSpace probes for measuring mains equipment unless you really understand what you are doing; get it wrong and you will kill the scope, the probe, and yourself. The Dunning-Kruger effect is unforgiving
  • 10Mohm *10 “high impedance” probes don't exist, despite what you might have been misled into believing! Typically they are 1000ohms at 10MHz, and only 100ohms at 100MHz. When measuring 100MHz and above, use a 500ohm *10 “low impedance” Z0 probe
  • be aware of how
    • the probe and scope work together to limit the observable frequency and risetimes; see below
    • the probe's capacitance can affect the circuit you are testing, particularly with *1 probes
  • use a *1 probe for low-voltages, and a *10 probe for high frequencies
Scope Bandwidth
Probe Bandwidth 20MHz 40MHz 60MHz 100MHz 250MHz 500MHz 1000MHz
20 14MHz 24.7ns 18MHz 19.6ns 19MHz18.4ns 20MHz 17.8ns 20MHz 17.6ns 20MHz 17.5ns 20MHz 17.5ns
40 18 19.6ns 28 12.4ns 33 10.5ns 37 9.4ns 39 8.9ns 40 8.8ns 40 8.8ns
60 19 18.4ns 33 10.5ns 42 8.2ns 51 6.8ns 58 6.0ns 60 5.9ns 60MHz 5.4ns
100 20 17.8ns 37 9.4ns 51 6.8ns 71 4.9ns 93 3.8ns 98 3.6ns 100 3.5ns
150 20 17.7ns 39 9.1ns 56 6.3ns 83 4.2ns 129 2.7ns 144 2.4ns 148 2.4ns
250 20 17.6ns 39 8.9ns 58 6.0ns 93 3.8ns 177 2.0ns 224 1.6ns 243 1.4ns M12
500 20 17.5ns 40 8.8ns 60 5.9ns 98 3.6ns 224 1.6ns 354 1.0ns 447 0.8ns
1500 20 17.5ns 40 8.8ns 60 5.8ns 100 3.5ns 247 1.4ns 474 0.7ns 832 0.4ns HP10020A
  • equipment/oscilloscopeprobes.1440319463
  • Last modified: 6 years ago
  • by tggzzz