Conductivity: On-line analyzer MFD88


The MFD88 is a device intended for fixed installation in the industry. It supports up to 12 measuring points in any combination of the measurement types offered. The outputs are provided through current loops, output relays and a digital interface, suitable both for connection with usual control systems and for direct control of smaller technologies.

Measurement locations are equipped with so-called input blocks located near the sensors. This allows a distance of up to 1000 m between the sensors and the device, without affecting the reliability of the measurement. A single unshielded two-core cable with the possibility of branching is sufficient to connect all the measured points. Housing for sensors and input blocks is provided by a wide variety of different probes, designed to suit sites of different nature. The device also supports automatic sensor cleaning, temperature correction and supplementary temperature measurement for each location.

Output interfaces include four industry standard 0-20 / 4-20 mA analog current loops with configurable ranges, up to 4 relays (expandable to 8 using current loops), as well as a MODBUS / RS485 digital interface. It is thus possible to directly connect to common current loop based configurations, to directly control technological elements (such as various dosing valves, etc.), or just as easily to transfer the entire set of measured values to the control system via a single digital interface.

Interaction with the user is easy thanks to the high-contrast dot-matrix LCD display, which is easy to read in the dark and in the sun, and a simple menu-based system controlled by only 6 buttons. Easy-to-open transparent door and optional access codes provide a good balance between convenient operation and protection against harsh environments and interventions of unauthorized persons. Semi-automatic calibration procedures are useful for regular maintenance of the measuring set-up.

The installation options are quite wide. Thanks to a wide range of permitted temperatures, a high level of protection, an alternative power supply of 230V AC or 24V DC, a large permitted length of cabling and overvoltage protection applied to all interfaces (against the secondary effects of lightning), there is no problem placing the device almost anywhere. An additional protective cover is available for outdoor use (the MUT13V clamp).

Advanced functions include freezing of outputs during calibrations or sensor cleaning, to prevent interference with technology control during measurement downtime, data logging available for later review or download, storage of calibration data in the input block located in the probe, allowing easy relocation of the probe for maintenance or other use without loss of calibration, as well as a number of options for direct control of the technology via relays or current loops, with limiting values control, time delay and other widely configurable logic, or using integrated PID controllers with convenient automated settings.

The order must include a list of the required measurements and additional components, so that appropriate probes equipped with the correct sensors and input blocks can be supplied, as well as the correct device configuration for the setup.

Conductivity measurement

The MFD88 supports conductivity measurement using classic two-electrode sensors. Thanks to advanced technology, capacitive effects on the electrodes are eliminated, which makes the measured data accurate even at high conductivity values. With an installed temperature sensor TTK21, several preset profiles for temperature correction are available, or the appropriate linear coefficient can be entered. The output can also be converted to TDS or salinity values, either by a user-selected coefficient or by the PSS-78 method.

Automatic sensor cleaning

Automatic sensor cleaning may be used on a limited number of measuring points, if they are equipped with SPO41ME or SPR41ME probes and sensors suitable for automatic cleaning. The device controls the mechanisms of the individual probes, and freezes the respective values so that the output from the device is not affected by the ongoing cleaning process.

Power supply230 V 50 Hz, or 24 V DC ± 20 %
Power consumptionmax. 20 VA
Dimensions (cable glands not included)240 x 184 x 115 mm
Weightca 1.5 kg
EnclosureIP 65
Operating temperature-20 to +50 °C, input block -20 to +70 °C
Relative humidity10 to 90 %
Analog outputs4x loops 0 - 20 or 4 - 20 mA, configurable transfer from measurement display
Analog outputs loadPassive, max. 500 Ω
Relays2x or 4x built-in relay
(further relays 12V/20mA may be connected to analog outputs)
Contact rating (built-in relays)max. 3 A at 230V/50Hz, max. 5 A at 24V DC
Temperature measurement range-2 to +100 °C (also limited by installed sensor)
Temperature measurement accuracy± 0.2 °C
Conductivity measurement range30 µS/cm, 300 µS/cm, 3000 µS/cm, 30000 µS/cm, 30 mS/cm, 200 mS/cm (or up to 1000 mS/cm with special sensors)
Conductivity measurement accuracy± 2 % (of full range)
Temperature correction for conductivity measurementLinear coefficient 0 - 10 %/°C or preset profiles
Conversion of conductivity to TDS or salinityCoefficient 0.25 - 1.5 or the PSS-78 method
Automatic cleaningmax. 4 measuring points
Automatic cleaning intervalConfigurable from 1 min. to 24 hrs.