<< Click to Display Table of Contents >> Navigation:  Editing a SpecView Project > Editing GDWs - Graphical Display Windows > Variables List > Variables List - Properties

 

Use Variable List Properties to:

 

 

NOTE: If the required menu-item in the Variables List is not enabled (grayed-out) then go to the Online Features menu and choose Disable All (fully offline).

This is because some of the menu-items, such as changing instrument details can't be done while online.

 

Open the Variables List  by clicking  on the toolbar,

then, navigate to the Variable that you require:

 

 - For Instrument variables: Click the by the instrument's name.

 - For SpecView Variables: Click the by 'SV' to show the pre-defined variables.

 - For User variables: Click the by 'User Variables' and click the  by the type of the variable.

 

Then single-click the variable name to select it and click Properties, OR right-click the variable name and choose Properties from the popup-menu.

 

 

Name Information

Edits the names of variables such as alarms using the Variables Properties box

Example: Change 'Alarm 1 Status' to 'High Alarm'

 

 

Attributes

Check the Logged box to add a variable to Data Logging

Check the Alarm box to have SpecView monitor this boolean as an alarm; this option will be grayed-out if this variable is not a boolean type.

Check the Short List box to have the variable included in the Short List mode.

 

Note that the Logged, Alarm, Short List and Read-Only settings can be overridden by double-clicking in the boxes in the 'L', 'A', 'S', 'R' columns of the Variables List.

 

Checking the 'Apply ... To All' boxes will change those attributes on the same variables of ALL identical instruments in the project.

 

There is also an 'Automatically apply future changes via variable list columns to other similar parameters' checkbox. When this is checked it means that double-clicking in the columns of the Variables List to set or unset an attribute will also affect the same variables of ALL identical instruments in the project

 

 

 

Batch Tag

Text Variables and parameters can be marked as Batch tags.

Boolean settings

This allows the On/Off Labels (of booleans)  to be changed.

 

 

Scaling settings

Scales a number with decimals (real number) using the Variables Properties  box

A simple example is changing °C to °F:

Set the scale to 1.8 and the offset to 32

For a change like this it would also be appropriate to change the variable's name from, in this example, 'Temp C' to 'Temp F'.

 

 

For more complex scaling the formulas below allow you to work out the Scale and Offset values for parameters to convert between the readings available from instrument hardware into the values seen on the screen. SpecView always takes the instrument reading, multiplies by the scale and then adds the offset.

 

For example, for a 4-20mA signal coming into a sensor. This sensor converts the signal into a 0 to 4095 range inside the instrument. However, the values on the screen need to show 0 to 100% for this range.

 

The physical signal (4-20mA in the example above) does not form part of the equation because the instrument deals with that and provides a range of values (0 to 4095 in this case).

The equations for Scale and Offset convert from the 0 to 4095 instrument range into the 0 to100 User range.

 

InstLo to InstHi represents the range of numbers reported by the instrument. UserLo to UserHi represents the corresponding range of displayed values in the formulas.

 

 

 

Other common words for InstLo and InstHi are Full Scale Low and Full Scale High readings - they are the lowest and highest readings produced by the instrument and read into SpecView.  The InstLo and InstHi values can be determined empirically by setting the scale to 1.0 and the offset to 0.0 inside SpecView. Then, apply the lowest possible physical input to the instrument and note the value as InstLo.  Then apply the highest possible physical input to the Instrument and note that value as InstHi.

 

Examples:

1) It is quite common for many Chart Recorders to read numbers in the range 0 to 65535 for the pen range.  For example, a Pen's readings might be 0 to 100%, but over comms, this shows up as 0 to 65535.

InstLo = 0                InstHi = 65536        UserLo = 0                UserHi = 100

So, using the formulas above:

Scale = 0.001525902

Offset = 0.0

 

2) A 4-20mA input module where the 4-20mA range is represented by 0 to 4095 reading. User wants the range 0 to 100 displayed:

InstLo = 0                InstHi = 4095                UserLo = 0                UserHi = 100

Scale = 0.02442        Offset = 0.0

 

3) Same as example 2, but user wants the actual mA signal value displayed. This can be stated as:

A 4-20mA input module where the 4-20mA range is represented by 0 to 4095 reading. User wants the range 4.0 to 20.0 displayed:

InstLo = 0                InstHi = 4095                UserLo = 4.0                UserHi = 20.0

Scale = 0.0039072        Offset = 4.0

 

4) As for example 2, but the instrument reports back numbers as 1 decimal place, so: A 4-20mA input module where the 4-20mA range is represented by 0 to 409.5 reading. User wants the range 0 to 100 displayed:

InstLo = 0                InstHi = 409.5                UserLo = 0                UserHi = 100

Scale = 0.2442                Offset = 0.0

 

5) Similar to example 2, but the Instrument is physically capable of reading the whole way down to 0mA.  So, a 4-20mA input module where the 4-20mA range is represented by 820 to 4095 reading (because 0mA would read 0, but the lowest possible input signal is 4mA). User wants the range 50 to 100 displayed:

InstLo = 820                InstHi = 4095                UserLo = 50                UserHi = 100

Scale = 0.0152671        Offset = 24.96184

 

6) As a proof, consider converting a Centigrade figure into Fahrenheit. As we commonly know, C to F is multiply by 1.8 and add 32.  In order to check this fits with the formula:

Assume the centigrade range is 0 to 100 (Freezing point to Boiling point). This is the Instrument range. We know that the equivalent Fahrenheit values are 32 and 212. This is the User range.  So:

InstLo = 0                InstHi = 100                UserLo = 32                UserHi = 212

 

Applying these values to the formula:

 

 

 

7) Fahrenheit to Centigrade:  the opposite of example 6:

InstLo = 32                InstHi = 212                UserLo = 0                UserHi = 100

Scale = 0.555555        Offset = -17.7777

 

Note: It is useful to test values at both ends of the range and if any other values are known then try those too.

 

For example, the values produced in example 6 (C to F) are as expected, 1.8 and 32.  In example 7 though, the numbers don’t seem to make sense.  To test that they are correct:

 

Note: SpecView will multiply by the scale then it will add the offset, therefore:

First, 32'F:      32 * 0.555555 + (-17.7777)   =   0.0001 (which is approximately zero)

Next, 212'F:        212 * 0.555555 + (-17.7777) = 99.9989  (which is approximately 100)

And one other value that is known, -40 reads the same in C as F:

-40 * 0.55555 + (-17.7777) =   -39.9997

 

 

Saved Value

This tab is only shown when in Edit mode Offline (it is not shown while Online).

The frequency in seconds that values are saved is specified in SETTINGS.INI in the [RUNTIME] section as: AutoSaveUserVars=3600

(the default setting is 3600 seconds, which is once an hour).

If there are a large number of SpecView User Variables, then do not save them very often as this will slow down the system, especially on heavily loaded computers. The values are automatically saved whenever SpecView goes offline or is exited.

 

 

 

Group

Instruments, parameters and variables can be assigned to a group to keep them together logically: