This product is no longer available and has been replaced by: SDM8X50.
SDMX50 50 Ohm Coaxial Multiplexer with Enclosure
Services Available
Repair Yes
Calibration No
Free Support Yes


The SDMX50 is available in a very limited supply. The SDMX50 will be replaced by the SDM8X50.

The SDMX50 is one of three 50 ohm, coaxial, 8:1 multiplexers that can be used in a TDR100-based system. It consists of a surge-protected multiplexer circuit board mounted in a 10" x 12" x 5" environmental enclosure. The enclosure's backplate provides a strain-relief point for the coaxial cables. Cable ties and desiccant are included. 



Outside Dimensions 40.4 x 29.2 x 17.5 cm (15.9 x 11.5 x 6.9 in.) with mounts
Inside Dimensions 25.4 x 30.4 x 12.7 cm (10 x 12 x 5 in.) for enclosure
Weight 4.4 kg (9.8 lb)

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 SDMX50: 6

Expand AllCollapse All

  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).

Case Studies

California: Coastal Slope Monitoring
The North County Transit District (NCTD) of San Diego County, California, determined that three more
Australia: Rhizolysimeter Facility
The Charles Sturt University (CSU) Rhizolysimeter is one of the largest root-growth research facilities more
Ohio: Monitoring Sinking Highway
When the Ohio Department of Transportation (Ohio DOT) was preparing to widen Interstate 77, more
This Product Replaced

Privacy Policy Update

We've updated our privacy policy.  Learn More

Cookie Consent

Update your cookie preferences.  Update Cookie Preferences