Tinker & Rasor SR-2 – Soil Resistivity Meter

Tinker & Rasor SR-2 – Soil Resistivity Meter

The Model SR-2 Soil Resistivity Meter is an electronic instrument useful in finding the resistance of soil at various depths.

The instrument may be used with either two (2) or four (4) pins, which are set into soil in a straight line, at equal distances. The Pins are named C1, P1, P2 and C2. Voltages are driven between C1 and C2, while resistance drop is measured between P1 and P2 (4 pin method). In the two-pin method, the resistance drop is measured between C1 and C2 only. The distance between the pins is equal to the depth of the soil resistance.

The four (4) pin method has been standardized by ASTM (astm.org) as Standard G57-95(a), and this method is also described in NACE Internationals, Peabody’s Control of Pipeline Corrosion, Second Edition, pg. 84. (nace.org)

Testing methods include:

• Wenner 4 pin method
• 3 pin Fall of Potential
• 2 pin method
• Soilbox (lab) tests

Use with optional soilboxes

Tinker & Rasor offers two styles of soilbox: Model SB-1 and SB-2.

Model SB-1 conforms to the ASTM G-57 standard. Per ASTM G57, section 3.4: when using the 4 Pin method on the SB-1, the multiplier is “1.349”. This formula is the Resistance in ohms times the cross sectional area of the box, divided by the inner pin spacing. When using the 2 Pin method on the Model SB-1, the multiplier is “1”.

Model SB-2 conforms to the AASHTO T-288, Fig. 2. The standard describes the method for determining the multiplier to use in this application: 6.67 cm.

Soilboxes manufactured by a company other than Tinker & Rasor will use a multiplier determined by that manufacturer. It may be necessary to contact that company to obtain the correct methodology and information.

Data logging with optional DL-1

The SR-2 has a convenient connection port for the Tinker & Rasor Model DL-1 data logger.

Connecting the DL-1 data logger to the SR-2 allows the operator to trap resistances within the DL-1 TRAC software.

Front panel layout