There are 3 wires connected to the sensor. You have the two (red & white) for the heater circuit. The signal wire is the black one. Leave it plugged to the green ECU wire and pull back the rubber boot enough to connect the meter lead. Meter set for 2V DC range.

The titania reads on a voltmeter about the same as the Bosch zirconia, but with a slightly wider range of 0.1V to 1.4V (lean to rich). With the engine at a warm idle, the signal should be cycling up and down almost faster than you can read.

Opinions:
Readings favoring the high or low end of the range would indicate a rich or lean mixture, assuming the sensor is accurate. A sluggish sensor that cycles slowly throughout the range could be due for retirement.
I believe the Titania is longer-lived than the Bosch, based on some research a couple of years ago. But I replaced mine preemptively at around 152K miles.

The lowest cost OEM replacement I've found (NTK 25002) is at Sparkplugs.com for $100 + shipping from CA.
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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.