Kolectric Covermeter This early transistor instrument is powered by a 9 volt battery. It is designed to measure the thickness of concrete over the steel reinforcing bars in buildings and other structures. The meter movement is open circuit, but the electronics appears to be in order as I have established that the current between the meter terminals varies with the movement of the detector coil over a steel bar. The firm still manufactures covermeters and other instruments for the construction industry. London, UK,date unknown.
This is one of many instruments collected by Jack Davidson C Eng FIEE which I have been given by Dr Graham Winbolt
Instructions on the lid
Inside You will see that I have now modified the original meter casing to accommodate a a RS components micro ammeter shunted with a resistor.
Printed circuit board