Usage of grounding resistance tester
1. Preparation for using a grounding resistance tester
(1) Familiar with the user manual of the grounding resistance measuring instrument, and should have a comprehensive understanding of the instrument's structure, performance, and usage methods.
(2) Prepare all necessary tools and accessories for measurement, and wipe the instrument and grounding probe clean, especially the grounding probe. Be sure to clean any dirt and rust on its surface that affects its conductivity.
(3) Disconnect the connection point between the grounding main line and the grounding body, or the connection point of all grounding branches on the grounding main line, so that the grounding body becomes an independent entity without any connection relationship.
2. Measurement steps using a grounding resistance tester
(1) Insert two grounding probes into the ground along the radiation direction of the grounding body at a depth of 400mm, 20m and 40m respectively, as shown in the following figure.
Diagram of grounding resistance test: a) actual operation b) equivalence principle
(2) Place the grounding resistance measuring instrument flat near the grounding body and wire it as follows:
① Use the shortest dedicated wire to connect the grounding body to the terminal "E1" of the grounding measuring instrument (three terminal measuring instrument) or to the common terminal (four terminal measuring instrument) after short circuiting with C2 and ".
② Connect the measuring probe (current probe) 40m away from the grounding body to the wiring button "C1" of the measuring instrument using the longest dedicated wire.
③ Connect the measuring probe (potential probe) located at a distance of ⒛ m from the grounding body to the terminal "P1" of the measuring instrument using a dedicated wire with the remaining length centered.
(3) After the measuring instrument is placed horizontally, check whether the pointer of the galvanometer points to the centerline, otherwise adjust the "zero adjuster" so that the pointer of the measuring instrument points to the centerline.
(4) Set the "magnification scale" (or called coarse adjustment knob) to the maximum multiple, and slowly turn the generator handle (the pointer starts to shift). At the same time, turn the "measurement scale" (or called fine adjustment knob) to make the galvanometer pointer point to the centerline.
(5) When the pointer of the galvanometer is close to balance (the pointer is close to the center line), speed up shaking the rotary handle to make its speed reach more than 120r/min, and adjust the "measuring dial" to make the pointer point to the center line.
(6) If the reading of the "measuring dial" is too small (less than 1) and difficult to read accurately, it indicates that the magnification scale is too large. At this point, the "magnification scale" should be set to a smaller multiple, and the "measurement dial" should be readjusted so that the pointer points towards the centerline and an accurate reading is taken.
(7) Calculate the measurement result, i.e. R ground="magnification scale" reading × Measurement dial reading.