I know of two ways to monitor frequency. One is to use one of tvb's PICs. That needs a good frequency reference, probably a GPSDO. The other is to use the PPS input on a Linux box. That uses the system clock so you meed a good NTP setup. Some of the APS family of UPS boxes will monitor the voltage. You can ask what was the min/max since the last time I asked? (as well as what is the current voltage) That's good enough to catch glitches. If you want to measure current, I'd start with a current transformer. I don't know of anybody using them for long term measurements. I've used them with a scope to look at startup transients. -- These are my opinions. I hate spam.