how to verify cal kit?

[electrolust]

If I buy a used 3.5mm mechanical cal kit on ebay, how can i verify it is still accurate?

[james_s]

I don't know what a mechanical cal kit is, but generally speaking the way to verify any sort of calibration instrument or standard is with by comparison using a more accurate calibration device or standard.

[joeqsmith]

I assume a SOLT for a VNA.  Just send it back to the manufacture and have them check it. 

[DaJMasta]

Aside from sanity checks to see if they are at least close (if your load looks like an open, for example, it's probably bad) and visually inspecting the connectors for damage, there's not much you can do without a calibrated instrument or calibration kit to check against.  You can use a connector gage to check the dimensions of the center pin, but if you're verifying performance, you need a standard to verify against.


Given the nature of these kits, especially for non-critical work using out-of-calibration instruments, a sanity check and inspection will probably do the job, but I would send it away for a cal lab to check it if I needed verification beyond that unless you've got a calibrated VNA with cal cal kit that is good enough to verify the performance of the kit in question.

[electrolust]

By the time I send it back to mfr, I suspect it will be a) cost prohibitive and b) take long enough to no longer be returnable.

What about measuring a known "DUT"? I have a capacitance standard but no paperwork for it, so I suppose that doesn't help but if I did have it characterized by another calibrated VNA, would that be a reasonable enough test? I do have a high precision resistor from a Z0 probe but perhaps that isn't as useful. Or if I made an RC filter, where I can measure R to 6.5 digits and thus determine C with some accuracy? I suppose I have to know f with some accuracy as well and I am not sure how well I can determine that.

I'm reluctant to buy new as good kits are so expensive, but I'm also reluctant to take a chance. Maybe the question I should ask is, if the connector is in good mechanical condition (under microscope), then is the kit likely to be within spec? Are they very ESD sensitive? I wouldn't think so.

[TheSteve]

You can verify it mechanically with a gauge set but really you'd need to measure it after calibrating the VNA with a known good kit.
I've done this recently myself. I calibrated with an ECAL and then measured all 6 standards in a Keysight 85033E kit. It is specified for 9 GHz but I measured it up to 26.5 GHz. The male load seems to meet the specs of the official 26.5 GHz kit, the female comes close and is in spec to 22 GHz or so. Overall I am pleased. Ideally you really want connectors that look to have no wear. What kit are you looking at?

[electrolust]

85033E

[TheSteve]

85033E

Hah, that is the kit I just tested. It will be for sale shortly if you're interested.