| | Home | Products | Software | Download | News | Search | F.A.Q. | | |||||
Classroom |
|||||
| Navigation |
|
|
Setting up scheduled measurements
The TiePie engineering measurement software features the possibility to schedule measurements and store them on disk. This is very useful when, for example, an interference glitch has to be measured. If you don't know when this glitch will occur, the auto disk feature provides the solution. When the glitch occurs, the auto disk function takes a measurement of the glitch and the data is stored on disk. The time and date of this occurrence are stored with the data as well.
To activate the auto disk function, first set up the oscilloscope to the appropriate settings (input sensitivity, sample frequency, record lenght etc.). Then, enter the Measure menu at the top of the software and select the Auto disk function. In the dialog that follows, a target disk, directory and a name for the files can be selected. Note that the file name can only consist of 5 characters, as the last 3 characters in the filename will be added by the software for a file serial number.
The trigger system of the oscilloscope has a time out function. When the input signal does not meet the trigger conditions within certain time, a trigger is forced. This is used to see an unknown signal. This feature can be unwanted in the auto disk function, therefore a Time out infinite tickbox is available to set the time out to infinite. Thus the oscilloscope will be waiting for the input signal to meet the trigger conditions.
When all settings have been completed, the Start button can be pressed to start the auto disk measurements. The measurements will be stopped again when the Stop button is pressed.
Example
For this example of the auto disk function, we will be measuring a power outlet using a differential probe. What we're trying to capture is when a voltage above the standard 325 peak voltage is measured. This requires the proper setup of the trigger system, the record length, the sample frequency and the channel sensitivity. Look at the Measuring a power outlet measuring example before you start this measurement, to make sure that you do not permanently damage the TiePie engineering measuring equipment!
Since we're trying to capture a signal that (mainly) consists of a 50 Hz sine wave, the sample frequency can be set fairly low, for example 50 kHz. This, in turn, allows for a decent horizontal resolution of 5000 samples. For the vertical axis, we will need to set the input sensitivity to a value where a glitch will not likely exceed the sensitivity setting. Using the auto sensitivity setting is not recommended. In this example, we will take a 4 V input sensitivity setting, which effectively allows for a 800 Volts peak voltage. Finally, we will need to setup the trigger system right to capture the data we're interested in.
We want to capture glitches that happen on top of the normal 325 Volts, so the trigger mode has to be set to the Outside window mode. Next, the 'window' has to be properly set up to allow the right signals to trigger the measurement. The level of the window has to be set to +325 and -325 Volts or a little above, to capture the signals that exceed this normal voltage. Setting the level can be done by dragging the top end of the trigger symbol to the desired position, or choose the Level Ch X ... submenu in the trigger system menu to allow for a more precise setup. The latter requires a little calculating though, since the trigger level corresponds to the input voltage of the measuring instrument terminal. For an 'effective' 325 volts, this results in a 325/800 * 4 = 1.625 Volts trigger level.
Setting the -325 Volts trigger position can be done by dragging the bottom end of the trigger symbol to the desired position, or by selecting Hysteresis Ch X .... In the latter case, the value that is expected there is not the negative input value, but rather the peak/peak voltage of the signal. Therefore, this setting should be set to double the positive trigger level, in this case 2 * 1.625 = 3.25 Volt.
All settings that are necessary before the measurement can be started, are now completed. The auto disk feature itself can now be started by selecting it in the Measure menu. Select a disk, a folder and a filename for the data you want to capture. In the image, the filename is 'DATA_' and the file(s) is (are) saved in C:\TIEPIE\Data\. The final setting is to enable an infinite time out to make sure that the measurement is only started when the glitch we're aiming for is appearing. Tick the box that has Time out infinite next to it. The measurement can now be started by pressing the Start button. A maximum of 999 measurements will now be taken containing signals in excess of the 325 volt normally present on the power line.
