Megger DLRO200-115, DLRO200-EN Operating Manual

DLRO® 200 High Current, Low Resistance Ohmmeter

USER MANUAL

GSAFETY WARNINGS

THESE SAFETY WARNINGS MUST BE READ AND UNDERSTOOD BEFORE THE INSTRUMENT IS USED.

n DLRO200 is supplied without a plug terminating the supply lead.

An appropriate plug must be fitted prior to use.

n The DLRO200 must be grounded (earthed) when in use.

If the ground / earth in the socket outlet being used to energise the DLRO200 cannot be relied upon, the instrument must be connected to a reliable

earth / ground via the large green and yellow terminal on the left hand side of the instrument. If no ground / earth is present the instrument will refuse to switch on and the display will remain blank.

n Circuits must be de-energised before testing.

The DLRO200 must only be used on dead systems. If the item under test has a voltage upon it greater than 10 volts ac peak or dc with reference to

ground the DLRO200 will indicate the presence of the voltage and prevent any tests being carried out.

n Testing inductive circuits can be hazardous:

The DLRO200 is a high power instrument, designed for testing resistive loads. It must NOT be used to test inductive loads.

n During use the DLRO200, its current leads and the sample being tested can become hot.

This is normal and is caused by the passage of high currents. Take care when touching the instrument, current leads, clips and the test sample.

n This product is not intrinsically safe. Do not use in an explosive atmosphere.

n Ensure that the power switch is always accessible so that power can be disconnected in an emergency.

n If this equipment is used in a manner not specified by the manufacturer, the protection provided by the equipment may be impaired.

CONTENTS

SAFETY WARNINGS 2

GENERAL DESCRIPTION 4

OPERATION 5

Main Menu Screen 5

TEST Menu 6

OPTIONS Menu 7

CURRENT Menu 9

Warning Messages 9

Entering Notes In The Memo Screen 9

Test Result Storage 10

Real Time downloading of test data. 10

TEST TECHNIQUES & APPLICATIONS 11

Test Sequence 11

Lead Resistance 11

Interference And Grounding The Sample 11

SPECIFICATIONS 12

SYMBOLS USED IN THIS DOCUMENT AND ON THE INSTRUMENT

 u Protective Conductor Terminal  s Hot Terminals

G Refer to the User Manual for more information

1 Power On 0 Power Off

cEquipment complies with relevant EU Directives

GENERAL DESCRIPTION

The Megger® DLRO® 200 is an a.c. powered low resistance ohmmeter deigned to measure d.c. resistances in the low milliohms or microhms using a maximum test current of 200 Amps d.c. The maximum test current available is dependent upon the power supply, the resistance of the test leads and the resistance of the item being tested. Full details are available in the SPECIFICATIONS section later in this book.

The power lead entry is located on the left-hand side panel and marked “100-265 V a.c., 10 A max., 50/60Hz” for the DLRO200, or ‘115 V a.c. 10 A max. 50/60Hz’ for the DLRO200-115. The main On/Off switch is located next to the power lead entry. All other controls are mounted on the front panel. Should the supply earth be inadequate the instrument will refuse to switch on, the display will remain blank. An additional earth terminal is provided on the left ahd side of the instrument.

200

Principle of operation

The required current is set before the test starts. When the TEST button is pressed, after a short delay the current increases to the set current, the voltage detected across the “P” leads is measured, and the current then reduces to zero.

Operation is controlled using the two-axis paddle and the menu system, which appears on the backlit liquid crystal display. The keyboard is used to set the desired test current and to add notes, which may be stored with test results in on board memory for later download via the RS232 socket provided. The measured resistance, the actual test current and measured

voltage are clearly presented on the display after the test is complete.

The use of a four terminal measurement technique removes the test lead resistance from the measured value although the use of lightweight current leads may prevent the DLRO200 from producing the full requested current. In this case the instrument will produce the highest current possible taking into account the resistance of the current leads and the item being tested.

Before a test may be started the potential test lead contact is monitored to ensure good contact is present. This reduces the chance of erroneous readings and prevents arcing at the contact point, which would otherwise damage the item under test and the test lead contacts. A resistance measurement takes approximately 10 seconds.

DLRO200 is supplied complete with a pair of 5 metre (16 feet) current leads terminated with large clamps, and smaller, lighter potential leads. Other lengths and terminations are available if required.

The large terminals C1 and C2 supply a low voltage (from zero to 5 volts) which is adjusted automatically to produce the desired current (from 10 A to 200 A). C1 is the positive terminal. This d.c. voltage is half wave rectified and unsmoothed in the DLRO200, the inductance of the test leads providing sufficient smoothing for the current. The DLRO200-115 has additional smoothing within the instrument.

P1 and P2 are voltage measuring terminals. P1 is nominally positive, but connections can be reversed without affecting the measurement. All four terminals are floating.

A warning will be given if dangerous voltages are connected to any terminal (C or P) with respect to ground.

OPERATION

Terminate the supply lead with a plug suitable for your circumstances.

Plug the instrument supply lead into a socket outlet and switch the instrument on using the On/Off switch situated on the left side of the instrument. The POWER lamp will illuminate, the instrument will display the firmware version number and perform a calibration check. If this is successful the display will show “CALIBRATED”. If the check fails the display will show “NOT CALIBRATED”.

DLRO 200 V1.00

MEGGER LIMITED

2002

INITIALISING HARDWARE

CALIBRATED

200

After a slight pause the display will change to the Main Menu screen.

TEST OPTIONS CURRENT

SET CURRENT 150 CURRENT LIMIT 200

23 TESTS STORED

21/03/02 15:13

200

MAIN MENU SCREEN

This screen provides access to the menuing system, through which you set up your instrument and choose the desired test parameters. Navigation of this menuing system is by means of the cursor control and Enter key.

At the top of the screen are the three main menu choices; “TEST”, “OPTIONS” and “CURRENT”.

Below this are details of the test current selected (SET CURRENT), maximum current to be allowed (CURRENT LIMIT), the number of stored tests and the current date and time.

To perform a measurement is straightforward.

1. Use the Left and Right arrows of the two-axis cursor control to highlight the TEST menu. Use the down arrow to select the required test type. Press Enter.

2. Use the Left and Right arrows of the two-axis cursor control to highlight the CURRENT menu. Use the down arrow to select SET and press Enter. Type in the desired current using the numeric keys on the keypad. When finished press Enter.

If the current you have set is greater than the current limit, DLRO200 will beep and clear the SET CURRENT field. Re-enter the desired current, if necessary increasing the current limit to a value equal to or greater than the desired level. (See separate topic for setting the current limit).

3. Connect the sample to be tested to the instrument terminals and press the TEST button. The different test types have slightly different connection requirements, which are detailed, in the sections below.

+ 10 hidden pages