The ‘multifunction’ digital micrometer is becoming very popular in recent times. The readings may be processed with ease. The push of a button can convert a reading from decimal to inch and vice versa. Any position of the spindle can be set to zero and the instrument can be used to inspect a job within a specified tolerance. The instrument can be connected to a computer or a printer. Most instruments can record a series of data and calculate statistical information such as mean, standard deviation, and range (Fig. 1).
Fig.1 Schematic of Digital micrometer
The instrument is recommended to be used along with a stand for ease of measurement. The spindle is made of stainless steel and measuring faces are carbide tipped for a longer life. A locking clamp ensures locking of spindle at any desired setting. A constant and low measuring force is ensured by the thimble mechanism. Most of the instruments have a least count of 0.001 mm. An LCD screen displays the reading with absolute linear scale with simple digimatic data collection for personal computer (SPC) data output. An easy push button control is provided to choose the various functions of the instrument.
The push buttons controlling the various functions are as follows:
1. ON/OFF: To power the instrument on or off.
2. IN/MM: To select either inch or metric system of measurement.
3. ZERO: To set the screen display to zero at any desired position.
4. HOLD: To hold the measurement taken until the push button is operated again.
5. ORIGIN: To set the minimum value for the micrometer depending upon its size; micrometer count commences from this value.
6. Alarm indicator: To indicate low voltage and counting value composition error.