【正文】 he usual construction, in fact the grounding of PLC way adopts the second grounding ways, as for electromagic interference: if the cabi is provided with a plurality of high power frequency converter, can be in the PLC power supply is installed in front of a singlephase power filter can be, generally designed in the inverter PLC near the front end are equipped with power supply filter. The interference effect of DC and AC equipment, can be connected together even if the DC and AC circuits because of some reason connectivity, because they are not the same as a loop ( grounding is not part of the loop ), will not cause damage to the equipment. People have AC220V power and DC24V circuit connected to it, but the equipment work remains normal. Digital and analog ground suggested separately ( unless you39。re a lowvoltage electrical equipment power supply voltage only a few tens of volts ), because the digital circuit belongs to positive and negative 5V,12V,24V level, are vulnerable to interference, and once the external abnormal voltage once the series will very possible equipment damage. I just go to work in the factory has a 1000 tons of SACMI press, because other equipment and digital ground causes the electronic facilities burned down last several times, Italy sent technicians ( just graduated from secondary school students ) and replacement equipment, conductor of the in situ dug a pit, buried a piece of ground the brass and the earthing filler, engage in a separate grounding. 3 Lightning proof grounding device for part of a concept (1) Lightning receiving device directly or indirectly accept the lightning rod ( flash ), such as lightning, lightning protection zone ( ), overhead ground wire and arrester. (2) lead: for the lightning current from the lightning arrester is conducted to the grounding conductor. (3) grounding: electrical equipment, tower grounding terminal and a grounding body or the zero line connected with the normally not currentcarrying metal conductor.(4) grounding body ( polar ): buried in the soil and directly touch the earth metal conductor, known as the grounding body. Divided into vertical grounding electrode and level of grounding body.(5): grounding device grounding and grounding. (6): grounding grid by vertical and horizontal grounding body position having discharge and pressure equalizing function work grounding device. (7): grounding resistance of grounding body or natural grounding resistance to the ground of the sum, a grounding device resistance, its value is equal to the grounding device of voltage to the ground and through the grounding body into ground current ratio. At the same time the grounding resistance of grounding device is a constant level indication. 4 The grounding device is easy to corrosion location mainly 4 (1) equipment grounding downlead and connecting screws。 (2) each welding head。 (3) cable channel equalizing zone。 (4) the horizontal grounding body,Anti corrosion measures,grounding body using copper, copper clad steel earth body or hot galvanized materials。 welding brush asphalt paint or powder coating。 use of cathodic protection. One, ground resistance test requirements: a. AC grounding, grounding resistance should be less than4 ohm。 b. Safety grounding, grounding resistance should be less than4 ohm。 C DC grounding, grounding resistance should be according to the puter system specific requirements determined。 lightning protection to D. Grounding resistance should be less than10 ohm。 e for shielding system if the joint grounding, grounding resistance should not be greater than1 ohms. Two, ground resistance tester ZC8grounding resistance meter is used for measuring the power system, electrical equipment, lightning and grounding resistance value. Also measuring low resistance conductor resistance and resistivity of soil. In three, the instrument by hand generator, current transformer, a slide wire resistor and galvanometer etc., all arranged in the plastic shell body, and the shell is convenient for carrying. Accessory auxiliary probe wires, installed in the accessory working principle of the voltage paring type. In four, before use to check whether the plete tester, tester prises the following device. In 1, ZC8 type grounding resistance tester, a2auxiliary grounding rods two root of 3,5m,20m,40m wire a Ground resistance tester, usually hand ZCXX series, including a short black lines, a20M line, a40M line, testing line connected at one end of a tested object whose the other end is connected with a shake table on each of two short connecting terminals, and the remaining 2terminal 20M line with P terminal,40M line C terminal to terminal, after the 20M and 40M line according to the ribbon (that is, to shake table for the endpoint of a triangle ) or linear pletely out, hit good probe. In the shake table select file and then to 120RPM speed swing table, side table edge with a shake shake table can dial0, until the pointer on a shake table center scale 0, with stalls multiplied by the dial corresponding numerical result this grounding grounding resistance. Wire grounding is an important electrical safety technical measures, the operation should be serious, serious, ply with the requirements of technical specifications, must not be careless. Therefore, correctly use the ground, normative hanging, remove g