Indicator (Or Readout) : A device for indicating a condition, a current or potential. Typical ones used on inspection instruments are galvanometers, meters both De Arsenval or digital, CRT or a warning light. (RP 5A5)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}