wahat is electronic instrumentation?

Answer 1

It could be the difference between computer operated (electronic) and direct current operated (electric).

Or in the "old days" (most youngsters won't remember this) we only had one form of instruments. They were the dial kind and had needles and a scale. Those were "analog" gauges meaning the distance the needle traveled was in direct proportion to the quantity it was measuring. The input was either direct current or gear drive.
Then they came out with digital instruments. These only showed a number quantity on a readout display. There were no needles or scales and they really weren't even gauges. The numeric display was only a representation of the calculated quantity for whatever was being measured; it had no correlation to the actual amount that was being measured. It had some type of electrical circuit or computer chip that calculated and sent the quantity to the display.

This was the beginning of modern day electronics.

P.S. In case you don't know what I'm talking about, here are some examples:
Clocks/Watches >>>> hands and a scale, now digital
Speedometers >>>> needle and dial, now digitial
Temperature/Fuel Gauge >>>> needle and dial, now digital
Voltmeter/Ammeter >>>> needle and dial, now digital

Answer 2

instrumentation is different from instrument, early days it was pneumatic or hydraulic systems were used to control process equipments example valve opening ,

presently same is used by electronics to control however the valve opening is done by pneumatic ( air operated)

Answer 3

Any piece of test equipment which contains circuitry for performing specialized measurements.