When the memory length is selected in the 'Memory' menu of the oscilloscope, the memory still appears to be at the previous length, i.e. it does not update. Why is this?
To change the memory length, having first selected the required length using the up/down keys, it is necessary to activate the new memory length by pressing the soft key marked 'Select' twice. The length which the machine is currently set to is shown at the top of the screen and pressing the 'Select' button once gives the message 'PRESS AGAIN TO CONFIRM' and only on pressing select for the second time does the memory length get changed to the new value.
Pressing the Volts/Div or position paddles does not seem to have any effect on the traces shown on the screen. What is the problem?
Check that the indicator below the Trace View button is indicating the correct set of trace numbers, i.e. 1-4 for traces 1 through 4 and 5-8 for traces 5 through 8. To move the signal being shown on trace 7, for example, the indicator should be showing 5-8. Now move the position paddle which is above the BNC input for channel 3. Trace 7 should move.
To set the indicator and the controls to the other four traces, press the Trace View button once. Remember, when the indicator shows 5-8 the controls will affect the traces 5 through 8 and will not necessarily correspond to the signal being input in the BNC below that control.
How are traces turned ON and OFF as there do not appear to be any buttons on the front panel of the instrument for this purpose? (Classic range)
The controls for turning traces on and off are not front panel controls but are menu controlled items on Classic instruments.
To bring up the traces menu press the button marked Trace Control once and then press the soft key next to the specific trace to turn it on or off - if either Main Only mode or Zoom Only mode is selected. In Main and Zoom mode then pressing the soft key for that trace will toggle through the choice of Main (M), Zoom (Z), Main & Zoom (M Z), or OFF. Main shows only the main trace; the position and Volts/Div paddles affect the input range of the input amplifiers. Zoom shows only the zoom trace; the position and Volts/Div paddles affect only the position and zoom factor of the screen image (i.e. not the input range of the amplifiers). Main and Zoom shows both the main and zoomed views of the input signal but the position and Volts/Div paddles operate in the same way as they do in Zoom mode.
In Zoom mode, if the input signal is within the range of the input amplifiers currently set but the zoom factor applied means that the signal goes off the display then amplitude measurements will still measure correctly. However, if the signal goes off the screen in Main mode (or the input signal is above the input range of the amplifiers currently set) then the waveform will be chopped by the input amplifier and any amplitude measurements may not be correct.
What does the Synchro-timebase unit on a DataSYS 770A do and how does it operate?
The Synchro-timebase is a unit which allows the timebase of an oscilloscope to adjust automatically with changes in frequency of the signal being input. It is particularly useful for keeping a steady picture when taking measurements from a piece of rotational machinery which can be changing speed quickly, but where the display on the oscilloscope must remain steady.
To use the Synchro-timebase unit to its full potential requires a degree of understanding and knowledge as to the nature of the triggering signal which is being input. For example, how many pulses are expected to be seen in one revolution; is a constant stream of pulses expected or pulses to be missing/extra pulses, etc. Below are a several points which are worth checking if difficulty is being experienced getting a stable trigger from the Synchro- timebase unit:
a) Make sure that the timebase of the oscilloscope is set to External in order that the signal from the Synchro-timebase produces the horizontal deflection. Also ensure that the trigger source is set to Aux so that the Synchro-timebase produces the trigger.
b) Ensure that the threshold adjustment is not out of range. This is adjusted by the rotary control on the front of the Synchro-timebase unit and the out-of-range light will illuminate if the threshold is set out of range of the input signal.
When using the DataSYS 7100 Power Analyzer in Power Analyzer mode a lot of the buttons do not seem to be having any affect. Is this correct?
This is the way in which the unit has been designed to operate in Power Analyzer mode since it has been designed specifically to be used as a pre-compliance tester to EN61000- 3-2. When in Power Analyzer mode, only the controls needed to make the EN61000-3-2 measurement are available to the user. This is so that the tests can be carried out automatically and with as little trouble as possible.
For something which is not covered by the requirements for testing to EN61000-3-2, use the unit in DSO mode where full functionality of the instrument will be returned. It is possible when in DSO mode to make all the same measurements that are made when in Power Analyzer mode plus others, with the exception of the ability to compare with live calculated limit lines.
Using the DataSYS 7100 Power Analyzer the FFT waveform of the current harmonics are appearing correctly on the screen but the limit line is not being shown. What is the reason for this?
Check that the current clamp is clamped around the correct wire (the live or line wire) and is clamped with the arrow in the direction of the current flow. It should only be clamped around one wire. It is not possible to take a current measurement simply by clamping the current clamp around the flex since the flex will contain both the live and the neutral; the effects of the currents in the two wires will cancel giving a zero (or near zero) reading of current. If the clamp is the wrong way round the current will be seen as a negative current and will be at least 180 degrees out of phase with the voltage, and no limit line will be produced. The Power Factor will also show a negative value. If this occurs simply turn the current clamp round so that the arrow faces in the opposite direction.