Specifications

Command Set 4-2
Data Structure
Many commands require additional data values to complete the command
definition as shown in the example commands in Table 4.1. The particular
data necessary for these commands is described in full in the complete
command descriptions.
The most common type of data used in commands and responses is analog
data. Analog data is always represented in the same format for all models
in the D1000 series. Analog data is represented as a nine-character string
consisting of a sign, five digits, decimal point, and two additional digits. The
string represents a decimal value in engineering units. Examples:
+12345.68
+00100.00
-00072.10
-00000.00
When using commands that require analog data as an argument, the full
nine-character string must be used, even if some digits are not significant.
Failure to do this results in a SYNTAX ERROR.
Analog data responses from the module will always be transmitted in the
nine-character format. This greatly simplifies software parsing routines
since all analog data is in the same format for all module types.
In many cases, some of the digits in the analog data may not be significant.
For instance, the D1300 thermocouple input modules feature 1 degree
output resolution. A typical analog data value from this type of module could
be +00123.00. The two digits to the right of the decimal point have no
significance in this particular model. However, the data format is always
adhered to in order to maintain compatibility with other module types.
The maximum computational resolution of the module is 16 bits, which is
less than the resolution that may be represented by an analog data variable.
This may lead to round-off errors in some cases. For example, an alarm
value may be stored in a D1000 module using the ‘HI’ command:
Command: $1HI+12345.67M
Response: *
The alarm value is read back with the Read High (RH) command:
Command: $1RH
Response: *+12345.60M
It appears that the data read back does not match the value that was
originally saved. The error is caused by the fact that the value saved exceeds
the computational resolution of the module. This type of round-off error only