On 29 July 2013 01:44, Joseph Gray <[email protected]> wrote: > I found that there are at least two cal labs in El Paso, which is > reasonably close to me. One, Techmaster Electronics has pricing listed (I > hate it when everyone says "contact us for a quote"). The other is > MetroCal, which lists no information at all. > > Has anyone used either of these companies? What is your opinion?
Like you, I am not keen on the "POA". I have never had any voltage things calibrated myself - my HP 3457A has not been caibrated for a decade or so. But I do have some of my RF things calibrated by Techmaster Electronics, as they were calibrated by them when I purchased them. One is a HP 8720D vector network analyzer and the other is a Agilent 85033E 3.5 mm calibration kit, which is used to calibrate the VNA. There are several things that make me very suspicious of Techmaster Electronics. 1) Agilent state the equipment to verify the performance of the 85033E VNA calibration kit is not commerically available, so one has to question how anyone else other than Agilent can do it. (In practice, I suspect it gets returned to Maury Microwave, who make it for Agilent). The 85033E's cal certificate lists what Techmaster Electronics used for the 9 GHz 3.5 mm cal kit, and I'm not impressed at all. They used a 6 GHz type N calibration kit, an HP 8510 VNA and a simulation package. It fairly clear to me that such a list of equipment is not able to properly determine if a 9 GHz 3.5 mm calibration kit is within the specs set by Agilent. I think one could get a reasonable degree of confidence in a VNA cal kit using a good VNA, the calibration kit and a *verification* kit. But that is certainly not a real calibration. I suspect the only way to really verify the performance would be using things like laser micrometers to make mechanical measurements of the standards - not electrcal measurements on a VNA. 2) My VNA was calibrated by Techmaster Electronics too. I note the calibration certificate says under the notes that optoin 010 was added. Now option 010 is a software option to enable the TDR functionality of the VNA. There are known hacks to add this, and a cal lab might well have other ways to add it, by entereing a software code. But I doubt option 010 was legally added, since the VNA is unsupported by Agilent and the option can't be bought. So basically my confidence in Techmaster Electronics is zero. I question their ability to calibrate things they issue cal certificates for, and I question their integrety. My HP VNA is due for cal now. It expired a few days ago and I have contacted Agilent to get it calibrated - I would personally not trust any other lab. That's not to say there are not other labs capable of calibrating an HP VNA, but there is not one I would trust. I would say a 5.5 digit DVM is probably easier to cal than a VNA or VNA calibration kit, so the fact I'believe Techmaster Electronics are issuing cal certificates for things they can't calibrate, it would not surprise me if they could do a decent job on a 5.5 digit DVM. Agilent will charge you $200 to do the DVM. Personally I'd pay the $200 and get them to do it, but its easy to say that when I'm not paying! As for what the different cals mean, I know in the case of Agilent VNAs, irrespective of what cal you order, the cal will use the same equipment, so you end up with the instrument working the same. What changes is whether you get documented uncertainties, guard bands, and in some cals one gets a report of its performance before calibration as well as after calibration. For me personally, the cheapest cal from Agilent is good enough, as I don't need the extra information and so don't want to pay a lot to get it. Dave, G8WRB _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
