This product is no longer available and has been replaced by: SDM8X50.
SDMX50LP 50 Ohm Coaxial Multiplexer with 10 x 12 Backplate (no enclosure)
Services Available
Repair Yes
Calibration Yes
Free Support Yes


The SDMX50LP is one of three 50 ohm coaxial, 8:1 multiplexers that can be used in a TDR100-based system. This multiplexer was designed to be mounted inside of a user-supplied enclosure. It consists of a surge-protected multiplexer circuit board attached to one end of a powder-coated backplate. The multiplexer circuit board extends about 5” (13 cm) from the backplate, resulting in an L-shaped unit. Holes in the backplate provide strain relief for the coaxial cables.



Strain Relief Bracket Dimensions 26.7 x 27.9 x 1.3 cm (10.5 x 11 x 0.5 in.)
Circuit Board Dimensions 24.9 x 12.2 x 4.6 cm (9.8 x 4.8 x 1.8 in.)

Power Requirements

Input Power 12 Vdc
Quiescent Current Drain < 1 mA
Current Drain during Switching ~ 90 mA (All multiplexers of the same level switch simultaneously for less than 1 s.)

Frequently Asked Questions

Number of FAQs related to SDMX50LP: 6

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  1. The clicking sounds come from mechanical relays making and breaking their contacts.
  2. No. All SDMX50-series multiplexers in a TDR100 system may be connected to the same 12 V power supply.
  3. These three multiplexers all use the same relay board, but the housing differs. The multiplexers are described side-by-side on page 2 of this brochure.

    The most popular model is the SDMX50SP, followed by the SDMX50.

  4. PC-TDR is a free download in the Downloads section of the PC-TDR web page.

  5. In applications where TDR probes are used to measure soil water content, the maximum distance from the TDR probe back to the TDR100/TDR200 (even through one or more multiplexers) cannot exceed 15 m (50 ft) when using RG58 coaxial cable; the CS605-L, CS630-L, and CS640-L TDR probes have an RG58 cable. When using low-loss coaxial cable, the distance cannot exceed ≈25 m (80 ft); the CS610-L, CS635-L, and CS645-L TDR probes have a low-loss coaxial cable.

    In slope stability and rock mass deformation applications, the maximum coaxial cable length should not exceed ≈1 mile (5,280 ft). The maximum combined length of all SDM cables in the system should not exceed ≈76 m (250 ft).

This Product Replaced

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