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Farnell 72-6800 Manual

20mhz dual trace oscilloscope
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20MHz Dual Trace Oscilloscope
MODEL: 72-6800
8272-68000MC1

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Summary of Contents for Farnell 72-6800

  • Page 1 20MHz Dual Trace Oscilloscope MODEL: 72-6800 8272-68000MC1...

  • Page 2: Table Of Contents

    CONTENTS PAGE 1. GENERAL……………………........…......……………. 1-1. Description…………………………………………………………………………………………………. 1-2.Feature……………………………………………………………………………………………………… 2. TECHNICAL SPECIFICATIONS.………………………………………………………. 3. PRECAUTIONS BEFORE OPERATING THE OSCILLOSCOPE…...….……………. 3-1.Unpacking the Oscilloscope….……………………………………………….…………………………… 3-2.Checking the Line Voltage………………………………………………………………………………… 3-3.Environment……………………………………………………………………………………………….. 3-4.Equipment Installation and Operation…………………………………………………………………… 3-5.CRT Intensity………………………………………………………………………………………………. 3-6.Withstanding Voltage of Input Terminals………………………………………………………………. OPERATION METHOD………………………………………………………………….. 4-1. Introduction of Front Panel……………………………………………………………………………… 4-2.
  • Page 3 5-3.Cleaning…………………………………………………………………………………………………….. 22 6. BLOCK DIAGRAM………………………………………………………………………... SAFETY TERMS AND SYMBOLS These terms may appear in this manual or on the product: WARNING Warning statements identify condition or practices that Could result in injury or loss of life CAUTION Caution statements identify conditions or practices that could result in damage to this product or other property.
  • Page 5 FOR UNITED KINGDOM ONLY NOTE As the colours of the wires in main leads may not correspond with the colours This lead/appliance must only marking identified in your plug/appliance, proceed as follows: be wired by competent persons WARNING The wire which is coloured Green & Yellow must be connected to the Earth terminal THIS APPLIANCE MUST BE marked with the letter E or by the earth symbol or coloured Green or Green &...

  • Page 6: General

    1. GENERAL 1.1 Description The 72-6800 oscilloscope is a portable-type, dual-channel oscilloscope with a bandwidth of DC to 20MHz, and maximum sensitivity of 1mV/DIV. The time base provides a maximum sweep time of 0.2uS/DIV. When magnified by ， t he sweep speed is 100nS/DIV. The oscilloscope uses a 6-inch rectangular type cathode-ray tube with red internal graticule.

  • Page 8: Technical Specifications

    TECHNICAL SPECIFICATIONS MODEL 72-6800 20MHz OSCILLOSCOPE SPECIFICATIONS 1.OSCILLOSCOPE Sensitivity ～ 5V/DIV, 10 steps in 1-2-5 sequence. Sensitivity accuracy ≤3% ( × 5 MAG : ≤5%). Vernier vertical sensitivity To 1/2.5 or less of panel-indicated value. ～ 2 0MHz ( × 5MAG: DC ～...
  • Page 9 MODEL 72-6800 20MHz OSCILLOSOPE SPECIFICATIONS CH1, CH2, LINE, EXT (CH1 and CH2 can be selected only when the vertical mode is DUAL or ADD . Triggering source In ALT mode, if the TRIG. ALT switch is pushed in, it can be use for alternate triggering of two different source.
  • Page 10 MODEL 72-6800 20MHz OSCILLOSCOPE SPECIFICATION Sensitivity 5 Vp-p (Positive-going signal decreases intensity). Frequency bandwidth ～ 2MHz. Z AXIS Input resistance Approx. 47K o h m . Maximum input voltage 30V (DC+AC peak, AC frequency≤1kHz). Waveform Positive-going square wave. Frequency Approx. 1 kHz.
  • Page 11 Line Power Requirements Operating Environment Accessories Voltage :AC115V, 230V ± 15% selectable Indoor use Power cord……..…..1 Frequency : 50Hz or 60Hz Altitude up to 2000 m Instruction manual……1 Power consumption :Approx. 40VA,35W(max) Ambient temperature: Probes………………...2 To satisfy specifications : 10° to 35 ℃...

  • Page 12: Precautions Before Operating The Oscilloscope

    3. PRECAUTIONS BEFORE OPERATION THE OSCILLOSCOPE 3.1 Unpacking the Oscilloscope The oscilloscope is shippied from the factory after being fully inspected and tested. Upon receiving the instrument, immediately unpack and inspect it for any damages that might have been sustained during transportation If any sign of damage is found, immediately notify the bearer and/or the dealer.

  • Page 13: 3-4.Equipment Installation And Operation

    re removing the fuse holder. 3.3 Environment The normal ambient temperature range of this instrument is 0° to 40°C (32° to 104°F). Operate of the instrument abover this temperature range may cause damage to the circuits. Do not use the instrument in a place where strong magnetic or electric field exists.Such fields may disturb the measurement. 3.4 Equipment Installation, and Operation Ensure there is proper ventilation for the hole vent in the oscilloscope case.
  • Page 14 If an AC voltage which is superimposed on a DC voltage is applied, the maximum peak value of CH1and CH2 input voltages must not exceed + o r - 300V, so for AC voltages with a mean value of zero volt the maximum peak to peak value is 600Vpp.
  • Page 15 Figure. 4-2...

  • Page 16: Operation Method

    4.OPERATION METHOD 4-1.Introduction of Front Panel CRT : POWER…………………(6) Main power switch of the instrument. When this switch is turned on , the LED (5) is also turned on. .INTEN……………………(2) Control the brightness of the spot or trace. FOCUS…………………...(3) For focusing the trace to the sharpest image. TRACE ROTATION……..(4) Semi-fixed potentiometer for aligning the horizontal trace in parallel with graticule lines.
  • Page 17 VARIABLE………(9)(21) Fine adjustment of sensitivity, with a factor of ≥1/2.5 of the indicated value. When in the CAL position,. Sensitivity is calibrated to indicated value .When this knob is pulled out (x5 MAG state), the amplifier sensitivity is multiplied by 5. CH1 &...
  • Page 18 SOURCE……….(23) Select the internal triggering source signal, and the EXT TRIG IN input signal. VERT MODE switch(14) is set in the DUAL or ADD state ,select CH1 for the internal triggering : When the source signal. VERT MODE switch(14) is set in the DUAL or ADD state ,select CH2 for the internal triggering : When the source signal.
  • Page 19 (Both TV-V and TV-H synchronize only when the synchronizing signal is negative.) Time Base: TIME/DIV……….(29) Sweep time ranges are available in 20 steps from 0.2 us/div to 0.5 s/div. X-Y : This position is used when using the instrument as an X-Y oscilloscope. SWP.VAR………..(30) Vernier control of sweep time.This control works as CAL and the sweep time is calibrated to the value indicated by TIME/DIV.
  • Page 20 Input terminal for external intensity modulation signal. CH1 SIGNAL OUTPUT….(35) Delivers the CH1 signal with a voltage of approximately 20mVper 1 DIV into a 50 - o h m termination.Suitable for frequency counting,etc.
  • Page 21 AC POWER Input Circuit: AC Power input connector……(36) AC power input socket .Connect the AC power cord (supplied) to this connector. FUSE & line voltage selector….(37) Fuse rating is shown in Page 5. Line voltage selector to select power sources. Studs……………………………(38) Studs for laying the oscilloscope on its back to operate it in the upward posture, Also used to take up the power cord .

  • Page 22: 4-4.Dual-Channel Operation

    After setting the switches and controls as mentioned, connect the power cord to the AC line outlet, and then,continue as follows: 1) Engage the POWER switch and make sure that the power LED is turned on. In about 20 seconds, a trace will appear on the CRT screen.
  • Page 23 Figure. 4-4 Changet the VERT MODE switch to the DUAL states so that trace (CH2) is also displayed (The explanation in the proceeding section is of CH1). At this state of procedure,the CH1trace is the square wave of the calibrator signal and the CH2 trace is a straight line since no signal is applied to this channel yet.

  • Page 24: 4-5.Add Operation

    4.5 ADD Operation An algebraic sum of the CH1 and CH2 signals can be displayed on the screen by setting the VERT MODE switch to the ADD state. The displayed signal is the difference between CH1 and CH2 signals if the CH2 INV push switch is engaged. For accurate addition or subtraction,it is a prerequisite that the sensitivities of the two channels are adjusted accurately at the same value bymeans of the VARIABLE knobs.Vertical positioning can be made with the POSITION knob of either...
  • Page 25 5 ms/div for complete frames (two interlaced fields) of video. TV-H Setting the MODE switch to the TV-H position permits selection of horizontal sync pulses for sweep triggering when viewing composite video waveforms. Horizontal sync pulses are selected as trigger to permit viewing of horizontal lines of video.A sweep time of about 10us/div is appropriate for displaying lines of video.The SWP VAR control can be set to display the exact number of waveforms desired.
  • Page 26 which has a periodic relationship with respect to the measured signal is used. Since the measured signal is not used as the triggering signal, the waveforms can be displayed more independent than the measured signal.
  • Page 27 (3)Functions of TRIG LEVEL control and SLOPE switch: A sweep trigger is developed when the trigger source signal crosses a preset threshold level. Rotation of the TRIG LEVEL control varies the threshold level. In the “+” direction, the triggering threshold shifts to a more positive value, and in the “-“...

  • Page 28: 4-7.Time/Div Control

    When the CHOP and the TRIG ALT switch are both engaged during dual-trace operation, synchronization of the display is not possible because the chopping signal becomes the trigger.Use the ALT mode by itself, or select CH1 or CH2 as trigger source. 4.7 TIME/DIV Control Set the TIME/DIV control to display the desired number of cycles of the waveform.
  • Page 29 4.9 X-Y Operation Figure 4-8 Set the TIME/DIV switch to X-Y position. Then the instrument works as an X-Y oscilloscope. Each input is applied to the instrument as follows X-axis signal (horizontal axis signal ) : CH1 INPUT. Y-axis signal (vertical axis signal) : CH2 INPUT.

  • Page 30: 4-10.Calibration Of Probe

    4.10 Calibration of Probe As explained previously, the probe makes up a wide range attenuator. Unless phase compensation is properly done, the displayed waveform is distortion causing measurement errors. Therefore, the probe must be properly compensated before use. Connect the 10:1 probe BNC to the INPUT terminal of CH1 or CH2 and set VOLTS/DIV switch at 50mV. Connect the probe tip to the calibration voltage output terminal and adjust the compensation trimmer on probe for optimum square wave (minimum overshoot, rounding off and tilt).

  • Page 31: Maintenance

    5.MAINTENANCE WARNING The following instructions are for use by qualified personnel only. To avoid electrical shock, do not perform any servicing other than in the operating instructions unless you are qualified to do so. 5.1 Fuse Replacement If the fuse blows, the power lamp indicators will not light and the oscilloscope will not operate. The fuse should not normally opened unless a problem has developed in the unit.
  • Page 32 Do not use abrasive cleaners on any portion of the oscilloscope.
  • Page 33 6.BLOCK DIAGRAM...

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