TI21 Test Meter (TTM) Operating Instructions
Contents
1. Ensure that low battery indication is not displayed if it is displayed replace the batteries If unit powers down automatically after 30 minutes it can be re activated by pressing the backlight button or by operating the main switch Track circuit frequency selection The frequency for operation for the track on which measurements must be set on main switch and an approximate voltage range must be selected on the range switch AC or DC measurement If broadband AC or DC measurements are to be taken the AC or DC position must be set on the main switch The unit is fully isolated from rail to rail voltages and protected from overload of the input Current measurement The TTM can be used to measure track circuit rail current in the running rails when a Rocoil rail current transducer probe is connected to the meter This allows a profile of the rail current to be recorded to aid fault finding particually for detecting where current leakage is occurring Details of the RCT is given in the RCT operating instructions BATTERIES The batteries are located in a compartment at the rear or the meter Access is achieved by releasing two screws and carefully lifting off the cover Ensure that the batteries are fitted correctly and are of the leak proof type Refit and secure the cover after fitting new batteries A low battery indication appears in the display when the batteries need to be replaced SIGNAL LEVELS OF HEALTHY AND FAILED TI EQU2. IPMENT Tables giving an indication of the typical minimum and maximum voltages or operating currents at different points in a track circuit can be found in the TI Manual Code of Prac tice or the ASTER Handbook It must be emphasised that these can vary depending on the particular site conditions and weather e g track ballast impedance However with the track circuits set up to operate with a 1 0 ohm shunt this will ensure a minimum of a 0 5 ohm shunt under all conditions which may subsequently occur Should the measured voltages differ considerably from the tables a fault must be sus pected In particular a check for a broken bond rail should be made if the drop shunt rises significantly It is recommended that when a track circuit is installed a complete set of measurements are made and recorded then any subsequent major deviations from these will indicate a condition which requires investigation MEASUREMENT HINTS Pole Zero Rejection Ratio This is the ratio of the track voltage measured at a pole tuning unit to the track voltage measured at a zero tuning unit Example If track voltage at pole is 4 9 V and at zero is 0 35V Rejection ratio 4 9 14 1 0 35 Typical values for voltages across the rails at the transmitter tuning unit position can be found in the respective Manual Code of Practice Handbook and will indicate the state of the transmitter output The receiver input current is measured by con
3. TI21 Test Meter TTM Operating Instructions Bombardier Part No 6 6 117465GXL SAFETY Observe all Safety Procedures that are in force for track possession and for working on or near the track High voltages may be present at track circuit rail connections Work must be undertaken only by qualified amp authorised personnel If the TTM is past the calibration date specified on its calibration label the TTM must not be used until it has been re calibrated Safety style test leads must be used i e test leads with a plastic shroud around the 4mm plug that connects to the meter INTRODUCTION The Tl21 Test Meter TTM has been designed to measure voltages at specific TI and ASTER SF frequencies It enables readings of track circuit parameters to be taken without corruption from other track circuits or interference at non T frequencies e g 50 60Hz It is intended for use as an aid to fault finding with TI and ASTER SF track circuits For normal setting up procedures please refer to the appropriate Manual Code of Practice Handbook The TTM can also be used to measure track circuit current in the running rails when used in conjuction with a Rocoil Rail Current Transducer RCT please refer to the RCT operating instructions note that an RCT is not supplied with the meter The meter is supplied with a carrying case and leads OPERATION TTM is switched on when main switch is moved from OFF position to AC DC ora frequency
4. battery saving after 30 minutes Automatic backlight cancellation after 30 seconds or at power down whichever is shorter Environmental conditions Temperature range 0 C to 40 C Relative humidity 0 to 95 non condensing Ingress IP54 Weight 0 46 kg Overall size 190 mm x 100 mm x 70 mm Accessories Soft carrying case Test leads Test clips Test probes Approvals EMC CE marked to EN 61326 LVD CE marked to EN 61010
5. necting the meter unit across the 1Q resistor terminals The meter reading then represents current i e 0 to 20mV range represents 0 to 20mA To check correct operation of the TI receiver it is best to check its threshold by using a shunt box across the rails and monitoring the input current until the output relay drops The value of current at which this occurs depends on the gain setting and manufacturing tolerances Typical values of input current for various gain settings can be found in the TI Manual Code of Practice SPECIFICATION Main switch positions OFF 1848Hz TI G AC Broadband 2445Hz TI H 1699Hz TI A DC 2296Hz TI B OFF 1996Hz TI C ASTER SF 2600 Hz 2593Hz TI D ASTER SF 2300 Hz 1548Hz TI E ASTER SF 2000 Hz 2146Hz TI F ASTER SF 1700 Hz 3dB bandwidth on filtered ranges 60Hz Rejection on filtered ranges gt 55cB at 600Hz of centre frequency 3dB bandwidth on AC Broadband range 5Hz 10kHz Input connections 4 mm terminals suitable for shrouded plugs Accuracy 10 of full scale Display resolution 3 1 2 digits Over range display Input signal ranges selected on Range switch 0 to 20 mV 0to 20 V 0 to 200 mV 0 to 200 V Oto2V Maximum input voltage 250 V ACrms 250 VDC floating with respect to earth Battery type 4 x AA LR6 Alkaline type recommended Battery life Approximately 60 hours Automatic power down
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