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Using the CRO for the First Time Here is the place where you will have the opportunity to run through the basic operation of a CRO in a few easy steps. Later on the opportunity will arise for you to participate in a couple of short tutorials that should be completed using the particular hardware in conjunction with this WWW site. Step One: Switching the CRO On O.K. this may seem simple, but the first step is simply the act of locating the power switch and turning the CRO on. Seems simple but just keep it in mind that somebody is going to have trouble dong this. Step Two: Ensuring the CRO is Calibrated Correctly Rotate both Gain Variable Controls and the Time Base Variable Control completely clockwise, or untill an audible "click" becomes apparent. Taking the action mentioned above allows us to be sure that the CRO is properlly calibrated and any readings taken are accurate. Step Three: Adjusting the Trace Position and Appearance (a) First we set the for both Channels A and B to GND. (this should allow us to see a horizontal line across the display) (b)The next thing that we do is use the Mode Selector to allow us to view channel A on the display. (c)Now that we can see the position of the trace we use both the Intensity and Focus controls to achieve a clear appearing trace. (d)Finally we move the trace into the center of the display using the both the Horizontal Position Control and the Vertical Position Control corresponding to Channel A. (e) Use the Mode Selector to view the trace of Channel B on thedisplay. (f) Repeat (d). (g) Finally to check that the above steps have been carried out correctly we can set the Mode Selection Switch to DUAL which will allow us to view both traces on the display. Now if both traces are in the exact same vertical and horizontal positions the display will seem to have only one trace visible. Step Four: Checking that the CRO is Triggered Correctly Before any measurements can be made we must ensure that the CRO is correctly triggered. The best way to do this is to follow the steps listed below.
(a)First check that the Trigger Level Control is set in the AUTO position. This is done by pulling the knob towards you. (c)Now we put the Slope Control to the Positive selection. (d)Ensure that the Sync Selector is in the A.C. position. (e)Finally make sure that unless otherwise advised, leave the Source Selector in the INT position. Step Five: Connecting the CRO to the Circuit It is most important, when connecting the CRO to make a circuit measurement, to remember that the CRO can only take readings of VOLTAGES. This means that the CRO should always be connected in PARALELL to the circuit element over which we are trying to find the voltage. We now need to select which device we will use to connect the CRO to the circuit. The two devices that we have to choose from are the X10 Probe and the Coaxial Cable. In almost all cases we will use the Coaxial Cable as the X10 Probe is only required when we wish to make extremely accurate readings. Step Six: Measuring the Input Signal O.K. now we that the CRO has been connected to the circuit we can actually adjust the view of the signal on the display to allow us to make an accurate reading. This is done by following the instructions listed below: (a) Select the input channel that we wish to view using the Mode Selector. i.e. if Channel A is required the Mode Selector would be in the CH A position, Channel B the CH B position and to see both of the input signals the Mode Selector would be in the DUAL position. (b)After selecting the input we wish to the AC-GND-DC Selector is moved from the GND position to the D.C. position. NOTE: It may seem that if an A.C. signal is being measured, the AC-GND-DC Selector should be set in the A.C. position. This is not neccessary unless there is a large D.C. offset in the A.C. input. So please avoid the temptation to use the A.C. selection. (c) At this point the Vertical Gain must be adjusted. This is adjustedto allow the signal to be viewed on a scale that is convienient. NOTE: Be sure to adjust the Vertical Gain Control that corresponds to the input channel that we are measuring a signal with. (d) The final step involves the adjustment of the Time Base Control. Here the control is rotated to the right or left untill the shape and period of the signal viewed on the display can be observed. NOTE:When a D.C. is being measured the Time Base Control does not need to be adjusted. Now that the signal can be seen at an appropriate size on the display we can actually find the Amplitude and Period of the input signal. This is done in the following manner: D.C. Signal Amplitude Simply count the number of divisions between the Zero Level and the level of the measured signal. Then multiply this number by the setting on the Vertical Gain Control. e.g.A signal covers 4.2 divisions with the Vertical gain setting on 1Volt/div gives us a signal amplitude of 4.2 Volts so the input signal is 4.2V DC. A.C. Signal Amplitude For an A.C. signal the amplidude is usually measured on a Peak to Peak basis. So we count the number of divisions between the positive peak of the signal to the negative peak of the signal and multiply this by the Vertical Gain Control setting. A.C. Signal Period To find the period of the signal count the number of divisions that one cycle of the signal "covers",then multiply this by the setting of the Time Base Control. Back
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Revised: 15 September 2004