Defining Default Units & Conversions

Vault EDC uses whichever Unit Definition Item you select as the default for that particular unit. For all other Unit Definition Items in that unit, you must define a Unit Conversion.

To set a Unit Definition Items as default:

  1. Navigate to your Study in Studio.
  2. In Browse view, open the Units tab.
  3. Click + New Unit to create a new Unit Definition or click into an existing Unit Definition.
  4. Fill the required fields.
  5. Create Unit Definition Items by filling the required fields and clicking + Add Unit Definition Item to add additional rows.
  6. Select the Standard radio button on the Unit Definition Item you want to use as by default.
  7. Click Save.

If your unit only has one Unit Definition Item, Vault automatically uses that Unit Definition Item as the standard.

Value & Translated Value

When a user enters data with a unit other than the standard (default) unit, Vault EDC translates the entered Value (value__v) in whichever Unit Value (unit_value__v) the user entered it by converting it into the default unit. This results in the Unit Value Translated (unit_value_translated__v). In this case, the “unit value” refers to the value chosen in the unit drop-down menu for a field, and “value” refers to the user entered numerical value in the field.

The Unit Value Translated value uses a Precision of 4 automatically. Design any rules that reference this unit appropriately.

Formulas for Unit Conversion

You can also use formulas to define unit conversions. Note that for unit conversions, you do not need to define the item because you define a unit definition for each Item. Instead, use $value__v. Use two underscores before the “v”.

Formula Grammar Version 1 (Studies created before 19R1 in April 2019)

Use value__v to reference the entered value in unit conversion formulas.

Formula Grammar Version 2 (Studies created after 19R1 in April 2019)

Use $value__v to reference the entered value in unit conversion formulas.

If you want to define the scale of a number used in a unit conversion, you must use the Round function in your calculation.

For example, the conversion of pounds to kilograms can be written as $value_v /2.204622622. For a 200 pound value, the translated value would be 90.718473993777244 kilograms. If you wanted to use the shortened 90.7 in this example, you’d enter Round($value_v /2.204622622, 1) in the Unit Conversion field.

See the Vault CDMS Formula Reference for a list of available functions and operators.

Example: Fahrenheit to Celsius

You can configure a Temperature unit definition to convert Body Temperature item entries from Fahrenheit to Celsius:

($value__v - 32)/1.8

Enter Unit Conversion formulas on the appropriate line item in your Unit definition.

Unit Conversion Formula

Hiding Unit Items

After you publish your initial Casebook Definition version, Vault no longer allows you to remove unit items from your unit.

If you need to hide a unit item from the unit drop-down for data entry users, select the Hide checkbox. Note that you cannot hide the Standard item.

Guidelines for Formulas

Vault handles formulas from left to right. For nested functions, Vault handles the sub-functions from left to right before handling the parent functions. Vault handles arithmetic and logical operators before other types of operators, following the standard order of operations. You can override the order of operations using parentheses.

Guidelines for Expressions

Use these guidelines for writing an expression:

  • Decimal points are periods, regardless of your Vault’s locale.
  • The maximum expression length is 1,500 characters.

Guidelines for Functions

Use these guidelines for adding functions to a formula expression:

  • Function names are case-sensitive.
  • Functions may have one or multiple arguments. Different functions allow different numbers of arguments.

Study Update Restrictions

After you publish the initial version of your Casebook Definition, Vault prevents you from making certain changes in any later versions you may create. If you were to make these changes, it could cause errors during the casebook amendment process.

See Study Update Restrictions for a list of disallowed changes and available workarounds.