MEWOI3900C Wireless Online Earth Resistance Tester,Ground resistance tester,GEO Earth Tester

INTRODUCTION

MEWOI3900C  Accessories

● Detector

  ● 9P wiring terminal

  ● Warranty card/Qualification card

  ● Paper Box

SPECIFICATION

Measurement Range & Accurancy

(Note: 23℃±5℃，below 75%rh)

Technical Parameter

Network Structure

• Wireless Network System (Self -Development Software)

Wireless network system through GPRS communication protocol to transmit data ,build up by the detector(built-in GPRS transceiver module), 【SIM communication card, monitoring software, power adapter, computer(above equipment need the user provide and secondary development)】 and other components for long-distance ground resistance monitoring., distance is not limited.

Principle & Application

• Measurement Principle

1.Earth voltage measurement adopts average value rectification method. 

2.Earth resistance measurement adopts rated current change-pole method.

That is, the AC rated current I (11mA Max，128Hz) flows between the measuring

object E (ground electrode) and the C (current electrode); Get the potential difference

V between the E and the P (voltage electrode), and then get the grounding resistance

value Rx according to the formula: R=V/I.

3.The working error (B) is the error obtained within the rated working conditions, which is calculated from the inherent error (A) and variation error (Ei).

       A： Intrinsic error                                                     E1: Variation due to position change 

E2：Variation due to power supply voltage change       E3：Variation due to temperature change     

E4：Variation due to interference voltage change            E5：Variation due to contact electrode resistance change

E7: Variation due to system frequency change              E8:  Variation due to system voltage change

• Wiring Connection & Measurement Method

1.First: the user needs to make auxiliary grounding poles P and C every 5 ~ 10 meters on the same straight line near the monitored grounding pole E. Auxiliary grounding pole should adopt grounding materials or stainless steel material, prevent rust and rot, the grounding resistance value as small as possible, the general grounding resistance requirements no more than 100 Ω, ground voltage is less than 10V, so as to ensure the accuracy of the on-line monitoring.

Secondly: according follow table to connect the detector, computer, power supply, etc. It`s better that the connection between the detector and the auxiliary earth pole secured by electric power wire (for later maintenance and disassembly), or by welding.

2.The grounding resistance on-line monitoring usually adopts the precise three-wire method, but also can use the simple two-wire method to test. The simple two-wire method is used to measure the grounding resistance by using the existing grounding electrode which grounding resistance value is smaller as the auxiliary grounding electrode and short-connecting the C and P interfaces. Auxiliary grounding rods C and P can be instead by metal water pipes, fire hydrants and others metal embedded objects, common grounding of commercial power systems or lightning protection grounding poles of buildings, etc. During measuring, pay attention to removing the oxide layer at the connection point of the selected metal auxiliary grounding body. Simple two wires method wiring connection as right side figure:

The simple method measure the grounding resistance, the tester reading is the sum of the grounding resistance of the grounded body to be measured and the grounding resistance of the commercial grounding body.

R=RX＋re

Which: R --- The tester reading value;

RX ---The grounding resistance value of measured grounding object;

re--- the grounding resistance value of a common grounding body such as a commercial power system.

Then, the earth ground resistance value of measured grounding body is:

RX=R－re

Use simple method to measure the grounding resistance, try best to select the grounding body with a smaller re value as the auxiliary grounding electrode, so that the detector reading is closer to the real value.

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