HP5316A universal counter
The 5316A is a 100 MHz universal counter which was built and sold by HP. Different options were available: for example an optional 1 GHz input channel, or an upgraded TCXO or OCXO reference oscillator. Mine came with the additional channel C (1 GHz input option) and the TCXO reference oscillator. I got my unit for 75 USD without shipping from an Ebay auction.
I had luck because the auction picture of the powered up counter showed an error condition, and because of this not much people were interested in the unit. But one picture of the back of the unit showed the reference frequency source selection switch: This switch was in the external reference frequency input position, and not at the internal one. I thought that this switch positioning could be the reason for a missing reference clock, and therefore also the reason for the shown error condition. I decided to take the risk and to bid for the unit. I won the auction, and when the universal counter arrived a quick test revealed that in fact nothing is wrong with the unit. The picture above shows the counter measuring the output signal of a 24 MHz crystal oscillator unit.
The build quality is very high as can be seen on the pictures above. The basic 5316A consists of two channels and allows to measure frequency, period, time interval, time interval average, time interval holdoff (delay) and ratio. Conversion of this unit for operation in the European power grid was not difficult: The power connector on the backside of the unit contains a small PCB which can be taken out, than can be rotated and oriented according to the needed voltage level, and then slided back into the connector. I have never seen this kind of system to change the line voltage level but it worked well. Other than that the conversion only consisted in changing the main fuse to the correct rating for 240V mains voltage.
