Measure type: Enlarging/Color Analyzer
A color analyzer is a type of darkroom meter that also measures color balance in addition to enlarging times. This is a simple unit (the big-brother PM2 had several memory banks).
To use it you first make a print from a negative you like. You place the sensor box under a spot on the negative and null out the meter–skin tone is a common one. Then you put in the next negative, put sensor on a spot that has skin tone (or something you want to come out the same shade of gray), and change the aperture until the meter nulls out.
You do something similar with the color, except that you use a diffiuser to blend all the colors together. You start with standard negative (or transparency) and make a print you like. Then you put the diffiuser under the lens, put the sensor under it, and for each color channel (cyan, magenta and yellow) you null out the meter. For your next negative you place the diffuser under the lens, put the sensor under that, and the meter tells you which filters you need to print it.
I haven't tried it for color (I got it after I quit doing color); I use it as a simple enlarging meter. The thing I like about it is that it has a small sensor (as opposed to my Omega) and it doesn't go night-blind like my Labosix.