Soil Resistivity Apparatus, Model 54, by Collins

The Model 54-A soil resistivity apparatus is lightweight, accurate and simple to operate.


The Model 54-A soil resistivity apparatus is lightweight, accurate and simple to operate. It lends itself equally well to spot checks of soil or water resistivity, or to detailed investigations typical of pipeline survey work.

The complete apparatus consists of a 40" calibrated hexagonal steel rod with handles and insulated tip, a compact AC resistivity bridge instrument in a leather carrying case, and an ear set for balancing a bridge by null method. The rod is simply pushed into soil to the desired depth and connected to bridge. AC resistance between the tip and body of rod is determined by balancing bridge and soil resistivities in Ohms-cc read direct on the dial.

The soil rod is made of cold drawn hexagonal steel with a hardened steel tip insulated by a nylon washer. The Connecting lead from the tip is brought up through the body of the rod to the insulated terminal. The other terminal is grounded to the body of the rod. Units are furnished complete with soil bridge, rod, case, ear set, connecting leads, and instructions.

The bridge weighs only 1 3/4 pounds and is neatly assembled in a 6" x 3" x 2 1/2" polished ebony bakelite case. The rod is lightweight yet rugged for field usage. It may be used with any standard resistivity bridge and is also very useful as a pipe locating and contact bar for taking pipe potential measurements and long line currents.


  • Range: 0-250,000 Ohms-cc
  • 40" rod-standard (50", 60", 72" optional)
  • Field calibration check
  • Pinpoint tuning
  • Operates on 9 Volt battery

Operating Instructions

With soil rod inserted in soil to be tested, connect leads to soil rod and binding posts on Model 54-A marked "LEADS" (#1). Plug ear set into jack marked "PHONES" (#2), flip toggle switch (#3) to "ON" position, bring tone to "NULL" by means of dial pointer (#4). The resistance of the soil will be the dial reading in Ohms per cc.

Test Function

  1. Disconnect leads from soil rod.
  2. Turn power switch (#3) to "ON".
  3. Push & hold test switch (#5) "UP".
  4. While holding, move dial pointer (#4) until tone "NULLS". Reading on dial should match test position value, if not, reset pointer.
  5. Push & hold test switch (#5) "DOWN".
  6. Repeat step #4. It is best to check the MODEL 54-A at both points.