I have now been disappointed three times with Ebay 720a's. All were DOA completely or failed self-calibration horribly. These 720a's were sold by individuals at around the $1000USD mark.
I can purchase a refurbished and guaranteed 720a for around $3000.00. If one is establishing a modest, and easy to keep in repair home metrology lab, maybe an older Fluke 5000 series calibrator is the way to go? The older calibrators are being offered, again by individuals, or surplus businesses, for around $950USD. The guaranteed working 5440b's go for $2000USD without calibration. There may be more hope, that a used calibrator, with its built in protective circuitry, can be purchased surplus with more success than the 720a. The 720a divider resistors are too easily cooked by idiots. In addition, from my own sad experience, the sealed "A" switch on the 720a has a much shorter lifetime than the open wafer switches. Thus, even the refurbished 720a may suffer an "A" switch failure shortly after the warranty period expires. IMHO, a 720a only makes sense if you buy new for business purposes. Why have I felt the need for a 720a? 1. My 731B calibration procedure calls out a 720a. 2. I have a Fluke 750 divider that I acquired to calibrate my HP3456A voltmeter. The 750 divider manual calls out a 720a for its calibration. 3. Procedure for calibrating my HP735A to 1v +/- 2ppm from my Fluke corp. calibrated 731b calls out a Kelvin-Varley Divider. Can a Fluke 5000 series calibrator take the place of a Kelvin-Varley divider in all of the above procedures? Suggestions Welcome, Stan _______________________________________________ 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.
