m_the0ry
02-06-2007, 08:55 PM
I am trying to use a generic multimeter as a pH meter. It started off as a novelty project and now it's my obcession.
Anyways, I heard that there is a linear scaling of voltage drop - for a standard multimeter set in voltmeter state - with pH. I found this hard to believe since pH is inherantly logarithmic, but I wanted to test it anyways. When I put the probes in a weak acid, the multimeter first read something on the order of 65mV, and then dropped off in a natural log fashion.
I can only figure that either the impedence on my cheap ass multimeter isn't enough for reliably measuring the small voltages in this condition (as 40-100Gohm is standard in a Ph meter).
Any ideas?
Anyways, I heard that there is a linear scaling of voltage drop - for a standard multimeter set in voltmeter state - with pH. I found this hard to believe since pH is inherantly logarithmic, but I wanted to test it anyways. When I put the probes in a weak acid, the multimeter first read something on the order of 65mV, and then dropped off in a natural log fashion.
I can only figure that either the impedence on my cheap ass multimeter isn't enough for reliably measuring the small voltages in this condition (as 40-100Gohm is standard in a Ph meter).
Any ideas?