TRANSMISSION MEASURING SET

Transcription

1 Page 1 USER MANUAL TRANSMISSION MEASURING SET MODEL NO: AFT 999/999A BENTRON POWER SYSTEMS 21/1, KEDARNATH CHATTERJEE ROAD, BEHALA KOLKATA

2 Page 2 TRANSMISSION MEASURING SET ( DIGITAL DECIBEL METER WITH OSCILLATOR) MODEL : AFT 999 RDSO SPECN. NO. IRS : TC-43/87 DECIBEL READOUT INPUT OUTPUT FREQUENCY INDICATOR LED FREQUENCY SELECTOR SWITCH OUTPUT LEVEL ADJUST BATTERY CONDITION MONITOR PRESS TO MEASURE RETURN LOSS INPUT IMPEDANCE SECTION OUTPUT IMPEDANCE SECTION POWER ON SWITCH OUTPUT

3 Page 3 INTRODUCTION : The Digital Decibel Meter with Oscillator Model AFT 999/999A is designed to measure Transmission line parameters of an audio frequency circuit. It has a digital Decibel Meter that measures the level of signal in VF range. It has also a built in oscillator with 12 spot frequencies, which covers the entire VF range. This is an essential instrument to measure different parameters of any transmission media like quad cable, microwave and underground cables. This instrument displays the signal level in AF range in an LCD display. The instrument is designed as per Indian Railways Standard specification (RDSO specification no. SPN/TC/43/87)

4 Page 4 2. DESCRIPTION : The instrument consists of mainly three subsystems namely. (1) An Audio Oscillator with 12 spot frequencies. (2)A Digital db Meter with LCD display. (3) Power Supply Unit with maintenance free rechargeable battery and charger. 1)Audio Oscillator : The audio oscillator gives output of 12 spot frequencies of 200, 400, 800, 1000, 1200, 1600, 1800, 2400, 3000, 3500, 4000 and 5000 Hz. Output level of the oscillator can be controlled by a multi-turn potentiometer. Output impedance of the oscillator has three values to match the impedance of the transmission line. 2) Decibel Meter : The decibel meter has an LCD display which indicates the input signal level in dbm. The input impedance of the decibel meter is also adjusted to match with the transmission line impedance.

5 Page 5 3) Power Supply Unit : The instrument has a built in rechargeable Li-ion battery and a charger. Battery gets charge when 230VAC is connected to the instrument irrespective of the ON/OFF switch is On or Off. 3 LEDs have been provided in front panel to indicate the condition of the battery. A push switch press to measure return loss is provided. To measure return loss of a cable the cable is connected to the terminals provided on the back side of the instrument and return loss of the cable is measured by pressing the push switch. While measuring return loss the oscillator level should be set at 0 dbm.

6 Page 6 SPECIFICATIOS: Oscillator : Oscillator output frequency : Spot frequencies of 200, 400, 800, 1000, 1200, 1600, 1800, 2400, 3000, 3500, 4000, 5000 Hz Output Impedance : 600 Ohms, 1120 Ohms & low ohms Output Level Voltage (around 470 ohms) : Adjustable from 40 dbm ohms to + 5dBm. Adjustment is done by a multiturn potentiometer. Level Meter : Display : 128x64 Graphic LCD display. Input impedance : High (>20 K Ohm) 600 Ohms +/-2% 1120 Ohms +/-2% MeasurementRange : -50 dbm to + 10 dbm. Accuracy +/-1 count with maximum error 5 mv rms Power Supply : 230V AC 50 Hz (+10%, -20%) & 5V DC Li-ion Battery inbuilt (Power Backup duration = 10 hrs. approx. for a fully charged battery) Indications : Power ON LED/OK LED Charge LED 12 Oscillator Frequency LED

7 Page 7 Mechanical : 11 (L) X 9 (W)X 4.5 (H) approx. Dimension Weight : 4 Kg approx. OPERATION: Front Panel Controls: ON /OFF Switch : When the switch is ON the instrument gets power from the built in battery. Oscillator Frequency Selection Switch Output Impedance Selection Switch Input Impedance Selection Switch : Any of the 12 spot frequencies can be selected by pressing UP/DN switch. : Any of the 3 push type ganged switch is to be operated to select the output impedance. (Low, 600 or 1120 Ohms) : Any of the 3 push type ganged switch is to be operated to select the input impedance. (High 600 or 1120 Ohms)

8 Page 8 Press to Return Loss switch : When the switch is pressed, Return loss of a cable can be measured. Charge LED OK/ON LED : This LED glows when battery gets charged from the AC source. : This LED glows when the ON / OFF switch is made ON and battery condition is OK Output Frequency Indicator LED : There are 12 indicator LEDs for each 12 different frequencies. At a time, only one LED glows, which represents that the oscillator is generating corresponding frequency