MPX15 Multiplexer

The Multiplexer MPX15 is designed specifically for use with the RM15-D and RM15 resistance meters when used with either a PA20 or PA5 probe array. It opens up a much wider range of arrays and applications compared to the use of single adapters . For example it allows parallel Twin arrays for much faster ground coverage or more detailed area coverage with virtually no time penalty, multiple Twin arrays (up to 6 different spacings) for depth investigations, simultaneous measurement using Twin and Wenner alpha, beta and gamma arrays etc giving different perspectives on buried structures.

The MPX15 is also fully programmable via the RM15/RM15-D, allowing the user to define and store 8 different programmed sequences, with 8 configurations per sequence. The auto-log mode of the RM15 can be used with the MPX15, making multiplexing totally automatic, surveys even  faster and more efficient, whilst reducing operator errors and fatigue. The multiplexer uses a matrix of solid state relays which results in a system of higher reliability, lower power consumption and reduced weight then would be possible with conventional reed relays.


The MPX15 is suitable for use with either the BASIC or ADVANCED RM15/RM15-D and is powered and controlled by the RM15/RM15-D expansion port. It has an on board microprocessor that decodes and acts upon the commands sent from the RM15/RM15-D. The survey tracking of the RM15/RM15-D expands to indicate the status of the multiplexer if more than one reading is being logged per station. Special menus on the RM15/RM15-D allow the user to select a measurement sequence or program their own. The A, M, N and B terminals of the RM15/RM15-D and an additional pair of remote probes are all controlled by the MPX15.

Logging of a multiplexed sequence can be performed by a single press of the LOG key. Alternatively, an auto-log sequence can be started by pressing the START key--this will record the first sequence but then subsequent re-insertions of the probe array will automatically initiate this process each time, so the operator has to do no more than move the array onto the next reading station. If conditions permit, and Fast auto-log is selected, readings can be logged at 4 readings per second, allowing very rapid data collection.


The RM15/RM15-D/MPX15 system has three different measurement or logging modes : Single, Parallel Twin and Multiple. The Single log mode has just one probe configuration per reading station - ie a conventional survey.

The Parallel Twin  log mode has two Twin configurations
of the same probe separation mounted side by side on the PA5 frame. For example, instead of covering the ground with just one 0.5m Twin, it is possible to effectively mount two 0.5m Twin configurations side by side, with their centres separated by 1m, on the the PA5. When multiplexed by the MPX15, this array almost doubles the speed at which the ground is surveyed, since two parallel traverses are effectively made at the same time. Alternatively the two 0.5m Twin configurations could be separated by just 0.5m, allowing a doubling of sampling density with little increase in survey time.

The Multiple log mode has more than one measurement configuration,
of either different type or different probe separation, mounted on the PA5. For example soundings could be made at each reading station, under the control of the MPX15, with Twin configurations at 0.5m and 1m, together with a 0.5m Wenner. Alternatively, soundings could be made with Twin configurations at 0.25m, 0.5m, 0.75m, 1m, 1.25m, and 1.5m separations. These measurements could be used to provide valuable depth response information. In addition, Wenner and Double-Dipole measurements could also be made at the same time.


MPX15 mounted on a PA5 frame, below an RM15

Multiplexer for RM15-D and PA20
Allows a wide range of configurations eg -
Parallel Twin for faster ground coverage or more detailed area coverage,
Multiple Twin for depth investigation,
Simultaneous configurations eg Twin, Wenner alpha, beta and gamma arrays.
Store up to 8 user defined programs.
Store up to 8 sequences per program.
Log up to 4 readings/s.

Some possible PA20 and MPX15 configurations

Multiplexed 0.5m, 1m Twin
Parallel and Multiple Mode

Multiplexed 0.5m Wenner and Double-Dipole

Solid state relay voltage rating
Solid state relay current rating
Solid state relay on-resistance
Solid state relay power handling
Power consumption
Case dimensions
Weight, inc leads and mounting plating

200 V
40 mA
160 ohms
325 mW
2-8 mA at 5V, array dependent
160 x 80 x 55 mm
0.4 Kg

Multiplexed 0.5m, 1m, 1.5m
Twin Aligned centres

( All components and specifications subject to change without notice )