Data Collection Using The Data Logger CVF2

Main When you run Analyse-Plus, you can open existing Data Logger files from your hard drive (File menu) or immediately connect to the Data Logger CVF2 and perform collections (sampling). Because the Data Logger has its own processor and memory, you can disconnect the computer from the Data Logger during a collection (depending on the length and sample period of the collection). If you print from this application and the computer is not needed for collection, software disconnection occurs automatically. In this case, if a printer is connected to the Data Logger's print-thru port, printing from any application can be done before, during or after a collection. The Data Logger can also be physically disconnected from the computer and continue to sample and collect data alone ("Standalone mode"), subject to its memory capacity.

This design suits both data acquisition and data logging needs. Fast sampling (1000 samples/sec on all channels with the Data Logger CVF2) with continuous streaming to disk is possible as well as standalone mode for long term collections.

Naturally, you can bring data into Analyse-Plus from many other sources. See Bringing Data Into Analyse-Plus and Sending It To Other Applications


TDB Channel setup includes enabling channels you intend to use, specifying the input range and conversion constants (Signal Lo, Signal Hi, EU Lo, EU Hi specify how to convert mV, mA or Hz to Engineering Units). The Description, Units, and Status are for documentation purposes only. The Tag pull-down list shows the Tag Data Base (pictured at right) -- a library of all the tags you have used. Once a new tag is entered, it need not be entered again.

The following input ranges are available on analog channels (1 thru 8):
            Range                 Resolution
        0 to 10000 mV       0.15       mV
        0 to   2000 mV       0.031     mV
        0 to     500 mV       0.0076   mV *
        0 to     100 mV       0.0015   mV *
-5000 to   5000 mV       0.15       mV
-1000 to   1000 mV       0.031     mV
  -250 to     250 mV       0.0076   mV *
    -50 to       50 mV       0.0015   mV *
        0 to       20 mA       0.00031 mA

* These ranges have a choice of an anti-aliasing hardware filter of either 500 Hz or both 500 and 4 Hz.
mV means millivolts, mA means milliamperes
The resolution is based on a "noise-free" input and the Data Logger's 16 bit analog to digital converter.
The frequency channel can measure either counts or frequency (Hz).

TRIGSET Collection can be started immediately or can be triggered by a set of events. This is called the Collection Trigger Criteria. For example, to detect a line blockage condition, you might want to collect data only when a pressure reading is high and a flow reading is low. To do this, enable clauses 1 & 2 and enter the channel numbers corresponding to the pressure and flow inputs. Enter the condition as one of:
Greater Than
Less Than
Inside Limits
Outside Limits

Select the corresponding limits in Limit A and Limit B in Engineering Units.
Select the logic operator to tie the clauses together -- one of:

Sequenced means the events have to occur in the order specified (clause 1 to 3 if all are enabled). Latched means they must have occured but in any order and they don't necessarily have to be true at the same time. "And" means the events must all be true at the same (any given) moment.

If you set the trigger type to "Post-Trigger", the collection starts after a delay from the moment the criteria are met. You can specify this from 0 msec to 49 days. This also allows you to start a collection at a specific time (unattended collection). Just enter a delay but do not enable any of the 3 clauses. If you set the Trigger Type to "Pre-Trigger", the collection starts in advance of the moment when the trigger criteria are met. This is done by keeping the samples in a circular buffer in the Data Logger while waiting for the trigger conditions. This is a powerful feature that helps determine the root cause of an event, especially considering that it works in Stand-Alone Mode (Data Logger can be disconnected from the computer and performs the collection alone).

The criteria is checked in the Data Logger once per msec (millisecond), whether or not a computer is still connected (a computer must always be used to initiate the collection and pass the criteria to the Data Logger). The green COL LED indicates whether the Data Logger is checking for criteria conditions, counting down the post-trigger delay, or actually performing the collection.

If you are performing a manual collection, you do not need to enter a criteria here.

The ability to perform a Triggered Collection allows for a wide variety of diagnostic applications. It allows observation of recurring but unpredictable failures. It allows concentrating a data collection around an event of interest rather than collecting continuously and manually searching for the event.

MONITOR The Monitor display is used to monitor a collection and all inputs. The instantaneous measurements of each channel are displayed in mV/mA/Hz/Counts along with the corresponding value in Engineering units. The collection status (Collecting, Idle, Waiting for Trigger, Trigger Delay) is displayed in the bottom left corner.


This display is used to setup and start a collection. Enter the Sample Period and Number of Samples to collect. The collection duration is calculated for you. Enter comments for documentation purposes. These comments are saved in each sampled data file (one file per channel per collection) and in the Log file (a summary of the channels used and tags collected for each collection run).

The data files are named according to a 3 letter prefix, a 4 digit number and a letter "a" (channel 1) thru "i" (channel 9). Each collection increments the 4 digit number.

If you check the "Triggered Restart" checkbox, a new triggered collection will be automatically started when the desired number of samples has been collected in the current collection. The Data Logger will begin checking if the measured signals meet the Trigger Criteria in the next millisecond (see 2 screen displays back.)

Regardless of whether or not you select "Triggered Restart", you can choose whether your first collection will start immediately (click on Start) or when the Trigger Criteria is met (click on Start on Trigger). If you want to start a collection at a specific time (unattended), just enter a Delay in the Trigger Criteria and click on "Start on Trigger".

The message "Stand-Alone Collection Is Possible" is displayed if the number of samples to collect will fit in the Data Logger's memory. This implies that the computer can be disconnected at any time and that it is safe to print through the print-thru port. If Stand-Alone Collection is not possible, the message "The Data Logger must remain connected during collection" will instead be displayed (as in the example above). In this case, you will be warned if you attempt to print from this application or disconnect the Data Logger (to prevent loss of sampled data).

When not in Stand-Alone mode, the computer will continuously stream the sampled data to the hard drive (for example, if you selected 100 million samples). In this case, the data is not saved in a single file. It will be divided according to the size you specify in the Settings Window (not shown) up to a maximum of 250,000 samples. In the example screen-capture above, one million samples will be collected so they will be divided into at least 4 files.

The Anti-Aliasing Filter is a digital (software) filter done by the CPU inside the Data Logger. It complements the 500 Hz analog (hardware) filter. Together, they make aliasing quite unlikely. The digital filter "strength" is configurable and is entered as a time constant ratioed to the sample period. This way, once you choose the ratio, you do not need to adjust it every time you change the sample period.

The Collection Status and time remaining in the collection are displayed in the bottom left corner.


Sampled data can be plotted as it is collected or after collection (from files on the computer's hard drive). The above plot shows sampled data as it is collected with 3 channels in use. The plot always shows all active channels (up to 9) stacked vertically with the same x-axis time scale. The y-axis is always displayed in Engineering units.

The right side of each plot shows the channel, tag, status and last sample collected for each channel.

The plot is normally automatically scaled -- you can directly enter values on the y and x axes for manual scaling. The precision (number of decimals) of the y-axis labels is also automatically set based on the magnitude of the values plotted. The scroll bar at the bottom allows you to scroll through collected data even while the collection continues.

The pallette in the lower right corner allows resetting of x and y axes (to automatic scales), to grab the trace and move it, or to zoom in. The zoom function allows zooming in the y direction ,the x direction, x and y, or with respect to a specific point. Whenever the x axis is changed for one plot, all other plots will follow the same x axis so that the plots are always synchronized.

Collection status, filename and the date/time when the collection was started are displayed at the bottom of the window. In the case of triggered collections, this refers to when the first sample was taken.

The buttons in the lower right allow you to display a grid, change the colour settings or toggle between the input channels and Math Channels. Math Channels are calculated based on input channels and the formulas you specify. For example, math channel number 1 may be calculated as:
s1*2 + (s2-47.2)/5 - exp(butterworth(l,2,1,0.24,s5))

About 50 math functions are built-in.

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