Why buyers choose it

Direct ppm reading

0–20 ppm at 0.1 ppm on a 3½-digit LED display.
Isolated 4–20 mA

The reading goes on to a PLC or recorder on an isolated current loop.

Temperature compensated

A Pt-100 sensor corrects the reading automatically from 10 to 50 °C.
Simple calibration

Zero in sodium sulphite, span in saturated water against the table supplied.

In detail

This meter reads dissolved oxygen directly in ppm, from 0 to 20 ppm at 0.1 ppm resolution, on a 3½-digit LED display, and passes the reading on as an isolated 4–20 mA signal. Accuracy is ±0.2 ppm ±1 digit.

The probe is amperometric: a gold and a silver electrode sit in an electrolyte tube filled with 7.5% potassium chloride behind a membrane, and the oxygen that crosses the membrane produces the current the meter reads. Membrane permeability changes with temperature, so a Pt-100 sensor feeds automatic compensation from 10 to 50 °C.

Calibration needs two solutions and no gas bottle. The zero is set with the probe in 2% sodium sulphite, and the span in saturated water against the saturation table supplied with the meter, which runs from 0 to 50 °C at normal pressure.

The membrane is the part that needs care: it must be free of punctures and kept clean of organic film, and the probe is washed weekly when it is out of use. The meter runs from 230 V AC ±10%, 50 Hz.