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Lab Equipment

Lab Equipment. Contents. +. +. DC = 0 to 20. DC = 0 to 6. +. DC = 0 to Vpos. DC Power Supply. The negative 0 to 20 volt supply is proportional (by an adjustable ratio of up to -1) to the positive supply. Vneg = (0 to –1) times Vpos.

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Lab Equipment

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  1. Lab Equipment

  2. Contents

  3. + + DC = 0 to 20 DC = 0 to 6 + DC = 0 to Vpos DC Power Supply The negative 0 to 20 volt supply is proportional (by an adjustable ratio of up to -1) to the positive supply Vneg = (0 to –1) times Vpos All three supplies share a common terminal, which is NOT connected to the power supply “ground”. This terminal should normally be connected to your circuit “ground”. Vpos Don’t use; connects to chassis and power line gnd

  4. + + DC = 0 to 20 DC = 0 to 6 + DC = 0 to Vpos DC Power Supply D C A B Vpos Since the COM terminal is isolated from the power supply ground, you are not limited to using point B for your circuit ground. If you use point A, C, or D as your circuit ground you can use series combinations of the three internal voltage sources to obtain voltages higher than +20V and lower than –20V.

  5. Digital Multimeter (DMM) Range is set automatically DC voltage DC current Power switch Resistance AC current AC voltage AC = RMS value of AC part of waveform only DC = value of DC part of waveform only To measure TRUE RMS value of the complete waveform, press both DC and AC

  6. Diode test (passes small current through diode and measures the resulting voltage drop) Connect the RED lead to the diode anode and the black lead to the cathode.

  7. Use the RATE switch to set the speed of measurement and the resolution of the displayed values: F = fast speed = low resolution M = medium speed = medium resolution S = slow speed = high resolution

  8. For current measurements, move the RED lead to a current input 10 AMP current input has low internal resistance and introduces the lowest error; use this input whenever possible 100 milliamp current input has considerable internal resistance and may introduce considerable error; use the 10 A input whenever possible.

  9. Function Generator Select waveform output Set frequency, amplitude, and DC offset

  10. Observe decimal point; ignore the commas To enter values, press “Enter Number”, then the number keys, then “Enter”

  11. When entering values, use these keys to define the units. Notice that voltage values can be defined as either RMS or peak-to-peak.

  12. Shift Enter > > > “SYS Menu” > “OUT TERM” > > Enter “50 OHM ” “HIGH Z ” If the amplitude of the waveform measured by the scope or digital multimeter does not agree with the amplitude shown on the function generator display, reset the output termination to “HIGH Z”

  13. Oscilloscope Always adjust the scope to obtain as large of a waveform as possible (to maximize accuracy) Function buttons Adjust the FOCUS and INTENSITY to obtain a clear, readable display. When not actively observing waveforms, turn down the intensity to extend the life of the scope screen

  14. The AUTO SET button helps the scope find the waveform, but it also sets the waveform signal coupling to AC (undesirable) After using the AUTO SET button, reset the waveform signal coupling to DC using the AC/DC buttons General Rule: ALWAYS use DC coupling on the vertical channels so that you can observe the complete (AC & DC) waveform

  15. The VAR controls must be in the CAL position for the display values to be valid

  16. Use the X POS control to start the scope trace at the left edge of the grid

  17. Set the zero volt positions for ch A and ch B to known positions on the grid, usually the center horizontal line, by first selecting GND and then adjusting the Y POS controls

  18. Example of Setting Zero Volt Reference Zero voltage reference line set to known point (usually center line, but may anywhere you desire) Once positioned, be careful not to change it. Trace starts at first vertical grid line

  19. Use these to set the vertical (voltage) values per division Use this control to set the horizontal (time) value per division vertical and horizontal values per division (cm) are shown on the display

  20. DIGITAL MEMORY mode must be selected to be able to use cursors and transfer waveforms to the computer

  21. Scope Cursors Use function buttons to control cursors

  22. Cursor Positioning Buttons Controls lower cursor Controls left cursor Controls upper cursor Controls right cursor RETURN key takes you back to the previous higher level

  23. Setting the Cursor Mode and Reference Channel Reference channel selection available only when both channels A and B are displayed cursor reference channel Use to turn cursors on/off and to select what they display (vertical measurement = voltage or ratio; horizontal measurement = time, phase angle, or ratio) RETURN key takes you back to the previous higher level Voltage cursor will use either channel A or B “voltage per division” setting, as selected.

  24. Value of differences between horizontal (voltage) cursors Value of difference between vertical (time) cursors Frequency computed from inverse of time interval (valid only if interval is one cycle)

  25. Scope Triggering The waveform on the scope display is drawn from left to right (repetitively), beginning at a point when one of the signals being displayed meets a specified criteria. This criteria is defined by the settings of the horizontal (time base) trigger controls: Mode - the standard mode is AUTO Source - which signal is being used to trigger the scope Coupling - normally P-P (AC), but sometimes DC gives more control Slope - the scope trace begins on the upward or downward slope of the wave Level - the voltage level of the wave at which the trace begins

  26. Sets the trigger mode (normally set to AUTO) Displays the trigger mode Sets the trigger slope Displays trigger slope Horizontal (time base) trigger controls Sets trigger coupling Adjusts the trigger level Displays trigger source and coupling Sets trigger source

  27. To capture a non-repetitive waveform, set the desired trigger conditions, select the SINGLE TRACE trigger mode, then press RESET to “arm” the scope. Single Trace Operation After the scope has been “armed”, a single trace will be drawn when the signal level matches the trigger conditions (slope and level) you have selected. The trace will remain displayed until you press RESET or transfer the waveform to the computer.

  28. Example Waveform Trigger level set to zero volts and a positive (upward) slope

  29. Example Waveform Trigger level set to +1 volt, with a positive slope Zero volt reference line

  30. Example Waveform Trigger level set to –1 volts, with a positive slope Zero volt reference line

  31. Example Waveform Trigger level set to zero volts, with a negative (downward) slope

  32. Delayed Trigger The trigger delay can be used to shift where the trigger point appears on the screen; this allows you to observe the waveform up to 10 divisions prior to the trigger point on repetitive waveforms.

  33. Waveform Zoom Use the X-magnification button to zoom in on part of the waveform; the magnification factor is changed each time you press the button.

  34. Move the display window Use the Display Part rocker switch to move the display window across the waveform image stored in the scope. (The scope stores two screen widths of data at X1 magnification)

  35. Trace Rotation Adjust to make trace parallel with horizontal grid

  36. Scope Probe Compensation Adjustment Make sure channel A and B signal coupling are set to DC Connect probe to calibration signal

  37. Scope Probe Compensation Adjustment Each probe has an adjustment screw that changes the compensating capacitor

  38. Scope Probe Compensation Adjustment Adjustment capacitor value needs to be increased until waveform is rectangular

  39. Scope Probe Compensation Adjustment Adjustment capacitor value needs to be decreased until waveform is rectangular

  40. Scope Probe Compensation Adjustment Rectangular waveform with correct probe adjustment

  41. Making Rise and Fall Time Measurements on Pulse Waveforms 100% 90% 10% 0% For rise or fall time measurements, use the 0%, 10%, 90%, and 100% lines on the scope grid

  42. Using the vertical scale control to set your waveform amplitude so that it is greater than the range of 0% to 100% Then use the var and the Ypos controls to line up your waveform with the 0% and 100% grid lines.

  43. 100% 90% 10% 0% The adjusted waveform display

  44. For rise time measurements Expand the waveform horizontally using the time base (TB) control Adjust trigger level to the 10% point or below Set trigger coupling to DC Set the trigger slope to positive (upward) for rise time measurements

  45. 90% 10% Adjust the vertical cursors so that they pass the 10% and 90% points on the waveform, and read off the rise time.

  46. For fall time measurements Expand the waveform horizontally using the time base (TB) control Adjust trigger level to the 90% point or above Set trigger coupling to DC Set the trigger slope to negative (downward) for rise time measurements

  47. 90% 10% Adjust the vertical cursors so that they pass the 10% and 90% points on the waveform, and read off the fall time.

  48. If scope fails to communicate with the computer: Use OPTION function button to check or correct communications settings OPTION IEEE IEEE-ADDR: 8 MODE: talker/listener If you have to correct the communications settings, cycle the scope power to reset the communications interface.

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