Hi, my name is Jack Marti.I started HJM ELECTRONICS in 1983.  At the time the only local company manufacturing good quality pH and conductivity instrumentation went out of business. Imported instrumentation was expensive and quite a few overseas suppliers stopped supplying goods to their local users due to international sanctions. The first order received was for the supply of 20 portable conductivity meters from CHEMSERVE SYSTEMS. A number of other projects followed, most of them reverse engineering of instrumentation that was no longer being supplied by the overseas manufacturers. I quickly realized that there was a mayor difference in the reliability and accuracy of different makes. The answer to these differences is in the way measurements are made and the methods of measurement used. After thorough investigation of the electrical, chemical and electro-chemical properties of liquids and how to measure these properties, I went and designed a range of pH and conductivity instrumentation that is made for South African conditions, works well, is reliable and can compete with imported products at a lower price.

pH instrumentation. We designed a unique pH measuring circuit that overcomes the problems created  by the high output resistance (500Mega Ohm) and low input signal output pH electrodes (0mV at pH7.00). In addition this circuit is encapsulated in a high-purity resin. This eliminates the problems of moisture and deposits on the circuit.   A unique drip-guard stops water running into the pH probe connector.Optical isolation of the pH probe signal from the measuring circuit eliminates ground loop errors.

Conductivity instrumentation.                                                                

Generating a regulated ac signal for conductivity measurement allows for accurate measurement. Automatic temperature compensation allows measurement over a 0-90 degrees C range.Optical isolation of the conductivity probe signal from the measuring circuit eliminates ground loop errors.

HJM ELECTRONICS supplies a large portion of pH and conductivity instrumentation to the water treatment industry in South Africa and the rest of Africa. We are continually updating and improving our products. We have replaced all of our instrumentation with microprocessor-controlled units. This allows us to use the same printed circuit board for more than one purpose. This cuts down on the amount of different boards to be held in stock.                                       

Some of the  boards use surface-mount components. This allows for more features to to be added to our products.