I discovered that analog VOMs are almost always low impedance. Tried reading an O2 sensor on my '73 RR and it kept reading 0 volts. Tried using a digital VOM and got the correct output voltage. I have an old analog sweep VOM I haven't used in years. Kept it around for testing TPS sensors.
There is a wide WIDE difference in non electronic VOM/ multimeters. I'm talking about the "traditional kind" that are not a VTVM (vacuum tube voltmeter) or a newer FET meter (transistorized meter with analog scale)
Look for the "ohms per volt". Back WAY back most old meters that first came out in the 30's--40's were only 1000 ohms per volt. These used a 1ma (1 milli amp) full scale meter. Some more modern meters by the late 50's --60's used 200ua (200 micro amp) meters and were 200,000 ohms per volt. Even those still "loaded" delicate circuits and were of no use in some circuits
