1 Inch NPT Thread Conductivity Probe Graphite Two Electrode 230mm Length Conductivity Sensor for Pipeline Mounting

The DEC790 is a 35 mm diameter, 230 mm long digital conductivity probe with a 1 inch NPT thread at both ends. That single mechanical detail is what makes the sensor so easy to deploy: the same probe can be screwed into a pipe tee as an inline transmitter, dropped into a sump as a submersible probe, clamped into a flow-through cell for sample lines, or fixed to a side wall bracket in an open channel. Plants that standardise on the DEC790 keep one spare part instead of four different mounting variants.

Inside the PPS body, a graphite two-electrode measuring cell reads conductivity from 0~20 µS/cm up to 2~10 mS/cm and reports the result as a digital RS485 MODBUS-RTU value. Automatic temperature compensation is applied internally, and the same probe also provides TDS (0~5 g/L), salinity (0~5 ppt) and water temperature (0.0~50.0 °C). No separate transmitter, no analog trimming, no shielded analog cable.

The sealed housing is IP68 rated and the probe weighs around 150 g without cable, so it can hang from its own cable in a wet well without extra support. The standard cable is 5 metres, and customised lengths of 10, 20 or 30 metres are available for deep tanks, remote outfalls and long pipe runs. The M16 cable gland keeps the cable entry watertight even after repeated re-termination in the field.

Installation conditions decide whether a conductivity sensor survives. The DEC790 is specified for the four mounting styles used most often in water and wastewater plants:

• Pipeline installation. Screw the probe into a 1 inch NPT tee at a low point of the run, where the pipe stays full and bubbles do not collect on the electrode.
• Submerged installation. Point the measuring face into the direction of flow and sink the probe deep enough to remain inside the moving water body, avoiding dead zones and sludge blankets.
• Flow-through installation. Fit the probe into a flow-through housing on a sampling line for clean, representative readings from a pressurised process.
• Side wall and flange mounting. Use a bracket or a flange adapter in open channels, tanks and basins where the probe must be reachable for cleaning.

Working pressure is up to 6 bar and the working temperature range is 0~50 °C, which covers the great majority of municipal water, sewage and light industrial duties. Keep the cable away from power cables and never bind the sensor lead to a motor or pump feeder, because electrical noise disturbs the measurement and damaged insulation can break down the measuring unit.

• One probe, four mounting styles. The 1 inch NPT thread at both ends supports pipeline, submersible, flow-through and side wall installation with standard fittings already stocked on site.
• Compact 35 mm body fits tight tapping points. A 230 mm overall length and 35 mm diameter let the probe fit small tee pieces, shallow channels and skid-mounted sample panels.
• IP68 PPS housing survives continuous immersion. The sealed polyphenylene sulfide body and M16 cable gland resist water ingress, mild chemicals and outdoor UV exposure.
• Digital RS485 MODBUS-RTU output eliminates analog loss. Longer cable runs are possible without signal degradation, and the value arrives at the PLC or SCADA already linearised and temperature compensated.
• Graphite electrodes resist fouling and polarization. The two graphite plates keep the reading stable in dirty water, which reduces cleaning frequency in sewage and surface water stations.
• Automatic temperature compensation built in. The probe compensates to a 25 °C reference internally, so no external temperature transmitter is required.
• Custom cable length for deep and remote points. Standard 5 m cable with 10 m, 20 m and 30 m options, which suits wet wells, outfalls and reservoir buoys.
• Low power, easy integration. Operating from 9~24 VDC at about 0.2 W, several probes can share one 24 VDC supply and one RS485 bus.

• Sewage treatment plants: inlet channel, grit chamber, aeration basin, membrane tank and final effluent.
• Water treatment plants and booster pump stations: raw water, filtered water and network monitoring points.
• Surface water stations: rivers, lakes, reservoirs and floating monitoring buoys.
• Industrial circulating water, cooling tower blowdown and boiler feed water supervision.
• Mining, metallurgy and paper mills: process water, thickener overflow and white water.
• Environmental monitoring projects and river basin supervision platforms requiring long cable runs.

The sensor uses a four wire connection: red for V+ power positive, black for V- power negative, white for RS485 data A(+) and green for RS485 data B(-). Default communication settings are address 17, baud rate 9600, no parity and one stop bit, and these can be changed through the Modbus register map. Measurement data is transmitted as 4 byte floating point values in little endian byte swapped order, so the Modbus master configuration must use the matching word order. Refer to the register table in the user manual before writing any parameter.

Only a monthly visual inspection and a monthly calibration check are required, and the interval can be relaxed once the trend is known. Clean the probe by shaking it in clean water. For heavy fouling, soak the measuring section in a mild detergent or weak acid for 15 minutes and rinse with distilled water. Never scrape the electrode surface with a hard object or wipe it with a cloth, because mechanical damage to the graphite surface forces a recalibration and in severe cases reduces the usable measuring range.