Megger DET3TA User Manual
  1. Manuals
  2. Brands
  3. Megger Manuals
  4. Test Equipment
  5. DET3TA
  6. User manual

Megger DET3TA User Manual

Det series earth ground electrode testers
Hide thumbs Also See for DET3TA:
Table of Contents

Advertisement

Quick Links

M
DET Series
EARTH GROUND ELECTRODE TESTERS
USER GUIDE

Advertisement

Table of Contents
loading
Need help?

Need help?

Do you have a question about the DET3TA and is the answer not in the manual?

Questions and answers

Related Manuals for Megger DET3TA

Summary of Contents for Megger DET3TA

  • Page 1 DET Series EARTH GROUND ELECTRODE TESTERS USER GUIDE...

  • Page 2: Table Of Contents

    CONTENTS CONTENTS INTRODUCTION SAFETY WARNINGS LIVE EARTH SAFETY PRECAUTIONS BATTERY INSTALLATION BATTERY CHARGING (DET4TCR2 and DET4TR2 ONLY) GENERAL DESCRIPTION PREPARATIONS FOR USE GENERAL OPERATING INSTRUCTIONS INSTRUMENT ILLUSTRATIONS BATTERY DESCRIPTION OF TESTS PREVENTIVE INSTRUMENT MAINTENANCE TECHNICAL SPECIFICATION REPAIR AND WARRANTY Symbols used on the instrument are: Caution: refer to accompanying notes Equipment protected throughout by Double Insulation Equipment complies with current EU directives...

  • Page 3: Introduction

    CALIBRATION ADAPTOR  TWO-CLAMP CALIBRATION ADAPTOR These instruments are designed and manufactured by: Megger Limited Archcliffe Road Dover Kent CT17 9EN England Megger Limited reserves the right to change the specification of these instruments at any time without prior notice.

  • Page 4: Safety Warnings

    Do not replace the rechargeable cells in the DET4TR2 and DET4TCR2 with non-rechargeable “dry” cells.  Do not use any other charging equipment other than that supplied by Megger for use with the DET4TR2 and DET4TCR2.  Do not operate the charging equipment supplied with the DET4TR2 and DET4TCR2 in damp or wet environments or outside.

  • Page 5: Live Earth Safety Precautions

    If the battery condition indicator does not show a full charge when battery cells are new, a cell may be reversed. DET4TR2 and DET4TCR2 ONLY Warning: Only use the cells recommended by Megger, part number 25985-031. BATTERY CHARGING (DET4TR2 and DET4TCR2 ONLY) Warning: Whenever battery cells are being recharged, there should be no connections to the instrument terminals and the instrument should be switched off.

  • Page 6: General Description

    GENERAL DESCRIPTION The Megger DET family of test instruments offers a unique solution to the measurement of earth or ground electrode (rod) resistance and soil resistivity. The family has seven variants supporting 2, 3 and 4- wire measurements:  The DET3TA provides 2 and 3-wire measurements and offers an analogue display.
  • Page 7 The DET family have the following features: Feature DET3TA DET3TD DET3TC DET4TD2 DET4TR2 DET4TC2 DET4TCR2 Automatic C ■ ■ ■ ■ ■ ■ stake check Automatic P ■ ■ ■ ■ ■ ■ stake check Manual P stake ■ check Automatic noise ■...
  • Page 8 Batteries – 8x AA (LR6) alkaline (except DET4TR2 and DET4TCR2)  Batteries – 8x AA (LR6) 1800 mA hr NiMH (DET4TR2 and DET4TCR2 only)  Warranty card  Calibration certificate (not DET3TA)  Owners CD-ROM manual  Tough polypropylene carrying-case ...

  • Page 9: Preparations For Use

    PREPARATIONS FOR USE Batteries The Megger DET series instruments are supplied with batteries fitted. When batteries become exhausted, refer to the section on battery replacement or recharging. Warning: Do not switch the instrument on with the battery cover removed. Inspection Before each use of the instrument, visually inspect the instrument case, test leads, stakes and connectors to confirm that their condition is good, with no damaged or broken insulation.

  • Page 10: General Operating Instructions

    Note: Some older versions of the DET3TC and DET3TD do not have the the 25V/50V button. The procedure for changing the output voltage is as per the DET3TA. Auto power down To extend battery life, the instrument will automatically switch off six minutes after the last operation.
  • Page 11 ICLAMP is not connected; VCLAMP is not connected [DET3TC, DET4TC2 and DET4TCR2 only].  Sufficient ICLAMP current [DET3TC, DET4TC and DET4TCR only].  Insufficient ICLAMP current [DET3TC, DET4TC2 and DET4TCR2 only]. Display symbols (DET3TA) Symbol Meaning Current stake (C Stake) resistance exceeds range for accurate measurement. OR Fuse blown.

  • Page 12: Instrument Illustrations

    INSTRUMENT ILLUSTRATIONS DET3TA Multi-function Test lead analogue display connections (at rear) Rc OK Resistance measurement settings (2P and Spike Selector switch button Battery check setting voltage setting Test button Resistance scale Voltage scale Potential test spike resistance indicator Battery charge...
  • Page 13 DET3TC Test lead connections (at rear) LCD display Resistance measurement settings (2P and 3P and clamp) Selector switch Voltage and current measurement settings 25 V/50 V output voltage select button Test button Warning – refer to Ruptured fuse Output voltage user manual Battery charge indicator...
  • Page 14 DET3TD Test lead connections (at rear) LCD display Resistance measurement settings (2P and 3P) Selector switch Voltage measurement settings 25 V/50 V output voltage select button Test button Output voltage Ruptured fuse Warning – refer to indicator indicator user manual Battery charge indicator Measuring range...
  • Page 15 DET4TD2 LCD display Test lead connections (at rear) Resistance measurement settings (2P, 3P and 4P) Selector switch Voltage measurement settings Test button 25 V/50 V output voltage select button Output voltage Ruptured fuse Warning – refer to Battery charge indicator indicator user manual indicator...
  • Page 16 DET4TR2 LCD display Test lead connection (at rear) Resistance measurement settings (2P, 3P and 4P) Selector switch Voltage measurement settings Test button 25 V/50 V output voltage select button Output voltage Ruptured fuse Warning – refer to indicator indicator user manual Battery charge indicator Measuring range...
  • Page 17 DET4TC2 LCD display Test lead connections (at rear) Resistance measurement settings Selector switch Voltage and current measurement settings Backlight control button Test button Frequency select button 25 V/ 50 V output voltage select button Warning – refer to Ruptured fuse Output voltage user manual Battery charge...
  • Page 18 DET4TCR2 Test lead LCD display connections (at rear) Resistance measurement settings Selector switch Voltage and current measurement settings Backlight control button Test button Frequency select button 25 V/ 50 V output voltage select button Ruptured fuse Warning – refer to Battery charge Output voltage indicator...

  • Page 19: Battery

    BATTERY Battery status indication (DET3TC, DET3TD, DET4TD2 and DET4TC2) The battery condition indicator is displayed whilst the instrument is switched on as shown: 100% battery charge remaining. 75% battery charge remaining. 50% battery charge remaining. 25% battery charge remaining. Some charge remaining, but instrument may auto power down at any time.
  • Page 20 Doing so will result in instrument damage and may cause personal injury. Only use the cells recommended by Megger. Warning: Only use the external charging equipment provided by Megger. To avoid the possibility of electric shock, switch instrument OFF and disconnect the instrument from any electrical circuits.

  • Page 21: Battery Replacement

    Defective/non-rechargeable cells detected or no batteries present. Defective/non-rechargeable cells detected or no batteries present. Charging terminated. Battery type DET3TA, DET3TC, DET3TD, DET4TD2, DET4TC2: 8 x AA (LR6) 1.5V Alkaline. Megger part number: 25511-841. DET4TR2, DET4TCR2: 8 x AA (LR6) 1.2V NiMH 1800mAhr.
  • Page 22 To avoid the possibility of electric shock, do not press the TEST button or touch the fuse when changing batteries. To remove the rear cover, release the screw at the bottom of the cover and lift the cover upwards. Remove the exhausted cells and dispose of in an appropriate manner. Refit new batteries of the correct type observing the correct polarity as marked on the battery compartment.

  • Page 23: Fuse Replacement

    The fuse blown status indicator is displayed whilst the instrument is switched on and performing a test as shown: Fuse blown. Fuse status indication (DET3TA) The fuse blown indication is given by the Rc LED when performing a test as shown: Fuse blown.

  • Page 24: Description Of Tests

    Suitable applications Where there is doubt about a particular application, reference should be made to the advice and guidance contained in the publication, “Getting Down to Earth” which is available from Megger, part number 21500- 072. The DET range of instruments can be used in agricultural locations (as per IEC 61557-5). In these circumstances, the output voltage should be switched to 25 V in order to comply with the standard.
  • Page 25 Principle of operation (three-terminal resistance measurement) The classic “fall of potential” test is used to accurately measure the resistance of an earth electrode using auxiliary stakes driven into the soil, which form a circuit for the test current injection and voltage measurement as used for the two-terminal method.
  • Page 26 By using a current transducer (the Megger ICLAMP) to measure the current flowing through the electrode under test as a fraction of the total test current injected, the instrument can determine the individual resistance.
  • Page 27 electrode under test is calculated as R=V/I2 or R=V/(I-I1). The current transducer (ICLAMP) measures I2 and feeds this value back to the instrument. Principle of operation (two-clamp stakeless resistance measurement) In this example, the electrode under test is connected to a network of other electrodes. It is either impractical or unsafe to disconnect an individual electrode for testing.
  • Page 28 Principle of operation (four-terminal resistivity measurement) The soil resitivity measurement works on a similar principle to the other measurements which use stakes: a current is injected around an outer loop and a voltage measured, shown in Figure 8. In this case, however, the measurement made by the instrument requires further conversion using a formula to derive the volumetric soil resistivity from the resistance value display.
  • Page 29 Measurement of ground noise voltage (DET3TC, DET3TD, DET4TD2, DET4TR2, DET4TC2 and DET4TCR2) Ensure the rotary selector switch is in the OFF position. Connect the instrument as shown in Figure 9. Figure 9: instrument connection for measuring ground noise voltage Potential stake Electrode DET3TD under test...
  • Page 30 Potential stake Electrode DET3TC under test Set the rotary selector switch to the position. The ground noise voltage reading will be displayed as shown in Figure 10. Figure 10: example ground noise voltage reading (DET4 display shown)
  • Page 31 40 V pk-pk (14 Vrms).  The instrument will display the warning triangle and an over-range condition above 100 V. Measurement of ground noise voltage (DET3TA) Ensure the rotary selector switch is in the OFF position. Connect the instrument as shown in Figure 11.
  • Page 32 Two-terminal resistance measurement (DET3TC, DET3TD, DET4TD2, DET4TR2, DET4TC2 and DET4TCR2) Ensure the rotary selector switch is in the OFF position. Connect the instrument as shown in Figure 13. Figure 13: instrument connection for measuring two-terminal resistance Metallic interconect Electrode DET3TD under test Metallic interconnect DET4TD2...
  • Page 33 Metallic interconnect Electrode DET3TC under test Set the rotary selector switch to the position. 25V/50V Select the desired test voltage using the button. DET4TC2 and DET4TCR2 only: Select the desired test frequency using the button. Press and release the TEST button (by holding the TEST button, the resistance measurement will...
  • Page 34 Figure 14: example two-terminal resistance reading (DET4 display shown) Note:  The test voltage used to make the two-terminal resistance reading is a.c. and may not be suitable for continuity testing according to some local regulations.  The instrument will display the warning triangle and an excessive noise voltage indicator if the ground noise voltage is above 40 V pk-pk (14 Vrms).
  • Page 35 Two-terminal resistance measurement (DET3TA) Ensure the rotary selector switch is in the OFF position. Select the desired test voltage using the procedure in the section on General Operating Instructions. Connect the instrument as shown in Figure 15. Figure 15: instrument connection for measuring two-terminal resistance...
  • Page 36 If the Rc LED does not illuminate following the pre-measurement checks, this indicates that the instrument fuse has ruptured. If the Rc LED illuminates solidly following the pre-measurement checks, this indicates that a two- terminal measurement can be made. The two-terminal resistance reading will be indicated on the scaleplate as shown in Figure 17. Figure 17: example two-terminal resistance reading Note: ...
  • Page 37 Three-terminal resistance measurement (DET3TC, DET3TD, DET4TD2, DET4TR2, DET4TC2 and DET4TCR2) Ensure the rotary selector switch is in the OFF position. Connect the instrument as shown in Figure 18. Figure 18: instrument connection for measuring three-terminal resistance Electrode Current stake under test Potential stake DET3TD...
  • Page 38 Electrode Current stake under test Potential stake DET3TC Set the rotary selector switch to the position. 25V/50V Select the desired test voltage using the button. DET4TC2 and DET4TCR2 only: Select the desired test frequency using the button. Press and release the TEST button [by holding the TEST...
  • Page 39 Figure 19: example three-terminal resistance reading (DET4 display shown) Note:  The instrument will display the warning triangle and an excessive noise voltage indicator if the ground noise voltage is above 40 V pk-pk (14 Vrms).  The instrument will display the warning triangle and a voltage over-range condition if the ground noise voltage is above 100 V –...
  • Page 40 Three-terminal resistance measurement (DET3TA) Ensure the rotary selector switch is in the OFF position. Select the desired test voltage using the procedure in the section on General Operating Instructions. Connect the instrument as shown in Figure 20. Figure 20: instrument connection for measuring three-terminal resistance...
  • Page 41 Figure 22: P stake resistance OK (green region) Figure 23: P stake resistance not OK (red region) If the P stake resistance is acceptable (needle in the green region of the scaleplate), release the button. Press and hold the TEST button.
  • Page 42 Figure 24: example three-terminal resistance reading Note:  No resistance reading is possible if the ground noise voltage exceeds 100 V.
  • Page 43 Three-terminal resistance measurement with lead null (DET4TD2, DET4TR2, DET4TC2 and DET4TCR2) In certain circumstances, the resistance of the test lead connecting to the electrode under test may itself form a significant part of the measurement electrode resistance. This effect can be eliminated using the lead-null technique described in this section.
  • Page 44 Press and release the TEST button [by holding the TEST button, the resistance measurement will be continually updated]. The instrument will perform pre-measurement check, the status of which will be indicated on the display. The three-terminal resistance with lead-null reading will be displayed as shown in Figure 26. Figure 26: example three-terminal resistance with lead-null reading (DET4 display shown) Note:...
  • Page 45 Four-terminal resistivity measurement (DET4TD, DET4TR2, DET4TC2 and DET4TCR2) The DET4TD2, DET4TR2, DET4TC2 and DET4TCR2 can be used to make soil resistivity measurements. The resistivity value can be derived from the four-terminal resistance reading made by the instrument and the particular separation and depth of the stakes. Ensure the rotary selector switch is in the OFF position.
  • Page 46 Figure 28: example four-terminal resistance reading (DET4 display shown) A soil resistivity value can be derived from the resistance reading and the stake geometry. Note:  The instrument will display the warning triangle and an excessive noise voltage indicator if the ground noise voltage is above 40 V pk-pk (14 Vrms).
  • Page 47 Measurement of ground current (DET3TC, DET4TC2 and DET4TCR2) Before measuring ground current, please follow the procedure contained in the section on ICLAMP calibration. Ensure the rotary selector switch is in the OFF position. Connect the instrument as shown in Figure 29. Figure 29: instrument connection for measuring ground current Installation earthing...
  • Page 48 Figure 30: example ground current reading (DET4 display shown) Note:  The instrument will display the warning triangle above 2 A – no ART testing is possible under this condition.  The instrument will display the warning triangle and an over-range condition above 20 A – no ART testing is possible under this condition.
  • Page 49 Three-terminal resistance measurement using ART (DET3TC, DET4TC2 and DET4TCR2) Before making a measurement using ART, please follow the procedure contained in the section on ICLAMP calibration. Ensure the rotary selector switch is in the OFF position. Connect the instrument as shown in Figure 31. Figure 31: instrument connection for measuring three-terminal resistance using ART Electrode Current stake...
  • Page 50 Press and release the TEST button [by holding the TEST button, the resistance measurement will be continually updated]. The instrument will perform pre-measurement checks, the status of which will be indicated on the display. The three-terminal resistance reading using ART will be displayed as shown in Figure 32. Figure 32: example three-terminal resistance reading using ART (DET4 display shown) Under certain circumstances, the instrument may display a noise warning as shown:...
  • Page 51  The instrument will display the warning triangle and a voltage over-range condition if the ground noise voltage is above 100 V – no resistance reading is possible under this condition.  The instrument will display the warning triangle above 2 A – no ART testing is possible under this condition.
  • Page 52 Three-terminal resistance measurement with lead-null using ART (DET4TC2 and DET4TCR2) In certain circumstances, the resistance of the test leads connecting to the electrode under test may itself form a significant part of the measurement electrode resistance. This effect can be eliminated using the lead-null technique described in this section.
  • Page 53 Figure 34: example three-terminal resistance reading with lead-null using ART (DET4 display shown) Under certain circumstances, the instrument may display a noise warning as shown: This means that interference has been detected which may impair the accuracy of the measurement. In particular, the reading could be lower than the actual resistance.
  • Page 54 Two-clamp stakeless measurement (DET4TC2 and DET4TCR2) Before making a stakeless measurement, please follow the procedures contained in the sections on ICLAMP calibration. Ensure the rotary selector switch is in the OFF position. Connect the instrument as shown in Figure 35. Figure 35: instrument connection for two-clamp stakeless measurement Close the ICLAMP around the conductor under test.
  • Page 55 Figure 36: example resistance reading using two-clamp stakeless method Under certain circumstances, the instrument may display a noise warning as shown: This means that interference has been detected which may impair the accuracy of the measurement. In particular, the reading could be lower than the actual resistance. The resistance of the electrode or system must be verified by an alternative method.
  • Page 56 ICLAMP calibration (DET3TC, DET4TC2 and DET4TCR2) The ICLAMP should be calibrated once at each test site to take into account the effects of transportation, temperature and humidity on the ICLAMP. Ensure the rotary selector switch is in the OFF position. Connect the instrument as shown in Figure 37.
  • Page 57 Figure 38: ICLAMP 100% calibration ICLAMP DET3TC Press and hold the TEST button until a “100” reading is obtained on the display. Switch the instrument OFF using the selector switch. The instrument is now calibrated to the ICLAMP and the calibration stored in non-volatile memory.
  • Page 58 OPERATION OF THE TWO-CLAMP CALIBRATION ADAPTOR Ensure the rotary selector switch is in the OFF position. Connect the instrument as shown. Close the ICLAMP around one loop of the two-clamp calibration adaptor. Close the VCLAMP around the other loop of the two-clamp calibration adaptor. Ensure a minimum separation of 100mm between the ICLAMP and VCLAMP.
  • Page 59 OPERATION OF THE CALIBRATION ADAPTOR Ensure the rotary selector switch is in the OFF position. Connect the instrument as shown. CALIBRATION ADAPTOR Set the rotary selector switch to the 2P, position. Press and release the TEST button [by holding the TEST button, the resistance measurement will be continually updated].

  • Page 60: Preventive Instrument Maintenance

    PREVENTIVE INSTRUMENT MAINTENANCE The DET series instruments require very little maintenance. Test leads should be checked before use to ensure there is no damage. Ensure batteries are removed if left unused for extended periods. When necessary, the instrument can be cleaned with a damp cloth. Do not use alcohol-based cleaners, as these may leave a residue.

  • Page 61: Technical Specification

    Battery type: DET3TA, DET3TC, DET3TD, DET4TD2, DET4TC2 - Instrument output: 8 off AA (LR6) dry cells Voltage: ±25 V or ±50 V at 128Hz (DET3TA, DET4TCR2, DET4TR2 – 8 off AA (LR6) NiMH DET3TC, DET3TD, DET4TD2 and DET4TR2) rechargeable cells...
  • Page 62 ICLAMP SPECIFICATIONS VCLAMP SPECIFICATIONS Measurement range: 1 mA to 1200 A Insulation: Double insulation Transformation ratio: 1000 : 1 Voltage rating: 600V CAT III Output signal: 1 mA / A (1 A @ 1000 A) Current rating: 1200A for 20 minutes Ingress protection: IP40 Accuracy 1mA to 100 mA : ≤3% of reading...
  • Page 63 CALIBRATION ADAPTOR ELECTRICAL SPECIFICATION Value: 25 Ω ± 0.1% MECHANICAL SPECIFICATION Operating temperature -10°C to +50°C / 14°F to 122°F 0% to 85% RH at +35°C / 95°F Storage temperature -20°C to +70°C (-4°F to 158°F) Dimensions: 60mm x 55mm x 25mm (2.5in x 2.25in x 1in) Weight: 0.1 kg approximately (0.2 lb) TWO-CLAMP CALIBRATION ADAPTOR ELECTRICAL SPECIFICATION...

This manual is also suitable for:

Det3tdDet4td2Det4tr2Det4tc2Det4tcr2Det3tc

Table of Contents