Monday, June 26, 2017

Another observation on test equipment

Years ago I bought myself a 4-channel 1 GHz digital oscilloscope. The four probes I got with it are the typical x10 passive type rated to 500 MHz. For my purposes this has always been good enough.

At work last week we needed to look at an async serial line at a weird bit rate of almost (but not quite) 10 Mbps. My co-workers found two very fancy digital oscilloscopes but couldn't find any probes to go with either scope. Noting that the simpler of these scopes was rated for 3.5 GHz I realized we wouldn't be looking for the normal cheap passive probes, and found a set of active single-ended probes rated for 3.5 GHz and another set of differential probes rated for 1 GHz, each carefully stored in custom carry cases. Selecting the appropriate probes for the job I cautioned my programmer co-workers to be careful with these probes, as they were probably worth $5,000 each.

Apparently that sounded like hyperbole to the youngest of my co-workers, but rather than disregard my caution he took the time to look for the going price for them. A couple of days later he told me that my $5K guess wasn't quite right: they're only worth $4,500 each. He said it in a matter-of-fact tone, but it was pretty clear that he was surprised that I really wasn't exaggerating as he'd thought.

This got me wondering what a 1 GHz active probe would cost for my scope. I found several such probes in used but calibrated condition for under $100 each. I've never really needed one, but now I'm wondering if I shouldn't buy one while they're available.

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