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Need help?Do you have a question about the Megger MFT1720 and is the answer not in the manual?
Provides a visual guide to the instrument's controls and indicators.
Explains the different elements shown on the instrument's display screen.
Details the physical connections and ports on the instrument's terminal panel.
Explains how to measure voltage, frequency, and determine phase rotation.
Describes the process for measuring resistance and continuity of conductors.
Details the procedure for performing insulation resistance tests.
Explains how to measure the trip times of Residual Current Devices (RCDs).
Describes how to measure trip current of RCDs using a ramp test.
Explains how to measure circuit loop impedance for fault loop path analysis.
Details the process for measuring R1+R2 impedance for protective conductor resistance.
Provides a visual guide to the instrument's controls and indicators.
Explains the different elements shown on the instrument's display screen.
Details the physical connections and ports on the instrument's terminal panel.
Explains how to measure voltage, frequency, and determine phase rotation.
Describes the process for measuring resistance and continuity of conductors.
Details the procedure for performing insulation resistance tests.
Explains how to measure the trip times of Residual Current Devices (RCDs).
Describes how to measure trip current of RCDs using a ramp test.
Explains how to measure circuit loop impedance for fault loop path analysis.
Details the process for measuring R1+R2 impedance for protective conductor resistance.
The Megger MFT1700/1800 Series Multifunction Tester is a robust instrument designed for comprehensive electrical installation testing. It is crucial for users to read and understand all safety warnings and precautions before operating the device, ensuring they are observed during use. The instrument is intended for use by suitably trained and competent persons, as mandated by health and safety legislation requiring valid risk assessments for all electrical work.
Before conducting insulation and continuity tests, the circuit under test must be switched off, de-energised, and isolated. For earth fault loop impedance, RCD, or earth testing, continuity of protective conductors and earthed equipotential bonding of new or modified installations must be verified first. Users should never touch circuit connections or exposed metalwork of an installation or equipment under test, as the system earth could become dangerously live under fault conditions. Similarly, avoid touching earth stakes, test leads, and their terminations during earth fault conditions unless adequate precautions are taken. The device includes 'live circuit warning' and 'Automatic discharge' functions as additional safety features, but these are not substitutes for normal safe working practices.
It is important not to move the rotary switch positions while a test is in progress. The instrument should not be operated or connected to any external system if it shows visible signs of damage or if it has been stored for prolonged periods in unfavourable conditions. Ensure the battery compartment or casing is closed, and all parts of the case (including keypad, selector switch, and display window) are present before operation. Always disconnect the instrument from all systems when changing batteries or replacing fuses.
For MFT1730 and MFT1835 models, do not replace rechargeable cells with non-rechargeable "dry" cells, and do not attempt to charge "dry" cells, as this can cause explosion or fire. The charging equipment supplied with MFT1730 or MFT1835 should not be operated in damp or wet environments or outdoors. All test leads must be removed from the instrument while charging. After insulation tests, capacitive circuits must be allowed to discharge before disconnecting test leads. The Insulation test ON lock should only be used when there is no risk of a circuit holding a charge.
The instrument should not be used if any part of it is damaged. Test leads, probes, and crocodile clips must be in good order, clean, and free from broken or cracked insulation. All test leads supplied are integral to the measuring circuit and must not be modified, changed, or used with other electrical instruments. A severed plug from the power cord must be destroyed due to the hazard of bare conductors in a live socket outlet. When testing, hands should remain behind the guards of probes/clips. U.K. Safety Authorities recommend fused test leads for measuring voltage on high energy systems. Replacement fuses must be of the correct type and rating; failure to use the correct fuse will result in damage during an overload.
Special precautions are necessary when "live" earths are encountered, requiring isolation switches and fuses (not supplied). When working near high tension systems (MV and HV), rubber gloves and shoes (not supplied) should be worn. In wet or agricultural environments, local safety standards must be observed, and test leads should not be touched with bare hands.
A 'Live' earth carries current from the mains supply or could do so under fault conditions. All involved personnel must be trained and competent in isolation and safety procedures. They must be instructed not to touch earth electrodes, test stakes, test leads, or their terminations if 'Live' earths are present. Wearing appropriate rubber gloves, rubber-soled shoes, and standing on a rubber mat is recommended. The earth electrode under test should be isolated from the circuit it protects before testing. If not possible, ART (Attached Rod Technique) may be used. Instrument terminals should connect to the system via isolation switches rated for maximum fault voltages and currents. The isolation switch must be open when personal contact is made with remote test stakes or connecting leads. Terminals should also connect via fuses rated for maximum fault voltages and currents.
The MFT1700/1800 Series features a clear display and intuitive controls. The instrument includes a left and right test button, a function button for lead null set, and a rotary switch for selecting primary functions. Secondary functions are also accessible. The display layout includes a touch voltage limit, an analogue arc, and function indicators. It shows battery status (NiMH or Alkaline), a secondary display, and primary results including phase rotation.
This function automatically displays AC Volts on the large display and frequency on the small display. For phase rotation, it indicates L1:L2:L3 as normal or L1:L3:L2 as reversed. The maximum voltage range is 600 Vac. There are no specific SETUP options for this mode.
This mode measures the resistance of conductors. It provides automatic measurement upon connection, showing resistance on the large display and test current on the small display. To null leads, connect them together and press TEST; a null indicator will appear. To remove nulling, open the circuit leads and press TEST. The buzzer can be turned ON/OFF, sounding below 2 Ω (adjustable in SETUP). Live circuit test is inhibited at 3 V. Test current options are 200 mA and 15 mA, with auto reverse testing On/Off. Continuity buzzer thresholds are selectable from 0.5 Ω to 100 Ω.
To start an insulation test, press and hold the TEST button until the measurement stabilises. Release the button to discharge the circuit. For Test Lock, hold down TEST and press LOCK; press TEST again to release. The insulation "Pass threshold" buzzer can be turned ON/OFF, sounding above 0.5 MΩ (adjustable in SETUP). Warnings include ensuring the circuit is disconnected and isolated, and a live circuit warning at 25 V or 50 V (default 50 V). SETUP options allow adjusting the insulation buzzer threshold from 0.5 MΩ to 500 MΩ (default 0.5 MΩ).
Press and release the TEST button to initiate RCD trip time measurement. The third lead can be connected for reverse polarity detection. Supply voltage ranges from 90 Vac to 280 Vac (L-E) and 90 Vac to 480 Vac (L1-L2). Functions include 0° and 180° (quick press), and Type AC, A, S, B selection (press and hold). 1700 series models automatically run 1/2xI, 1xI(0°), 1xI(180°), 5xI(0°), 5xI(180°). 1800 series models run 1/2xI, 1xI(0°), 1xI(180°), 2xI(0°), 2xI(180°) & 5xI(0°), 5xI(180°). The RCD VAR function allows adjustable RCD trip current. Warnings include touch voltage >50 V. SETUP options for touch voltage are 25 V and 50 V (default 50 V).
Press and release the TEST button to measure the trip current of an RCD. The third lead can be connected for polarity detection. Fast Ramp performs a Pass/Fail test between 50% and 100% of the range. Slow Ramp displays the trip current in mA. Warnings include touch voltage >50 V and reverse polarity. SETUP options for touch voltage are 25 V and 50 V (default 50 V).
Press TEST to start. L-E tests start automatically. Supply voltage ranges from 50 Vac to 280 Vac (L-E) and 50 Vac to 480 Vac (L-L, L-N). The Zmax function stores maximum loop measurements on the small display and the most recent measurement on the larger display. Warnings include over voltage and reverse polarity (with mains plug test lead). SETUP options allow auto start on connection ON/OFF. The third lead can be connected for reverse polarity detection.
Select Zref and make a measurement at Ze (or Zdb), which is automatically saved. Then, select R1+R2 mode and make a measurement as normal (Zs). Zref is automatically deducted from the Loop (Zs) value to give the R1+R2 value. To start, press and release the TEST button. Warnings include over voltage. There are no specific SETUP options for this mode.
The instrument is manufactured in the United Kingdom. Megger reserves the right to change the specification or design without prior notice. Megger is a registered trademark.
General| Type | Multifunction Tester |
|---|---|
| Insulation Resistance Test Voltage | 250 V, 500 V, 1000 V |
| Continuity Test Current | 200 mA |
| Earth Resistance Test | Yes |
| RCD Test | Yes |
| IP Rating | IP54 |
| Operating Temperature | -10 °C to +55 °C |
| Storage Temperature | -25 °C to +70 °C |
| Battery Type | Rechargeable Li-ion |
| Insulation Resistance Range | 0.01 MΩ - 1000 MΩ |
| PSC/PFC Range | 0 - 20 kA |
| RCD Test Currents | 10 mA, 30 mA, 100 mA, 300 mA |
| Frequency Range | 45 to 65 Hz |
| RCD Trip Time Range | 0 - 2000 ms |
| Display | Backlit LCD |
