pH/ORP Transmitter

One transmitter, two measurements. Fitted with a pH electrode it reads 0 to 14.00 pH; fitted with an ORP electrode it reads −2000 to +2000 mV. Temperature is measured alongside, 0 to 99.9 °C, and used for automatic compensation referred to 25 °C.

The reading leaves it on a galvanically isolated 4–20 mA output, optically coupled against interference, with RS485 Modbus RTU available as an option. Two alarm relays rated 220 V AC, 3 A switch at the high and low limits, and an optional flushing relay drives a solenoid valve to wash the electrode at intervals.

It is used in thermal power, fertiliser, metallurgy, environmental monitoring, pharmaceutical, biochemical and food plants, and on drinking water and swimming pools. For power stations it converts the pH of pure water and ammonia-dosed ultrapure water to the 25 °C reference those waters are specified at. It keeps 72 points, three days, of history and has a real-time clock, and its 128 × 64 LCD shows the time, pH or mV, temperature, output current and the alarm settings and states at once.

Accuracy is ±0.2 pH, ±1 mV and ±0.5 °C. The input impedance is at least 10¹² Ω, the electronic repeatability ±0.02 pH and the drift ±0.02 pH in 24 hours; the current output is within ±1% of full scale. It runs from 220 V AC ±22 V, 50 ±10 Hz, or 24 V DC as an option, in a 96 × 96 × 120 mm case rated IP54 that weighs 0.6 kg, at 0 to 60 °C and below 85% humidity. The electrode cable is 5 m as standard.