Setra System Model 595 - Manual (Page 8)

7.2.4 Setting Up a Custom Unit Scaling
Unit conversion performed by the 595 is of the form y=mx+c. Where units other
than the commonly used set provided are required then the m and c can be
written directly. This is achieved via the command aXUn, !. Note n
represents the variable to be written with the following value as detailed in
Table 7.
Table 7
Variables Used for Unit Conversions
Value of n Variable Written
0 Pressure Units Slope = m
` 1 Pressure Units Offset = c
2 Temperature Units Slope = m
3 Temperature Units Offset = c
The value of m should be calculated as follows:
For Pressure: m = (Full Scale in User Units – Zero Scale in User Units)
(Full scale in mH
2
O at 4 °C – Zero Scale in mH2O at 4°C)
For Temperature: m = (Full Scale in User Units - Zero Scale in User Units)
(Full Scale in °C – Zero Scale in °C)
The appropriate values can then be written as show in Tables 8 and 9.
Table 8
Setting the Pressure Units to mbar
Command Response Comment
aXU0,98.0665! a0 Sets the slope m to 98.0665, equivalent to mbar.
aXU1,0! a1 Sets the offset to 0 as 0 mbar = 0mH
2
O at 4 °C
Table 9
Setting Temperature Units to Kelvin
Command Response Comment
aXU2,1! a1 Sets the slope m as same as °C
aXU3,-273! a1 Sets the offset to -273 to read in Kelvin
7.2.5 Obtaining Maximum and Minimum Measurements
The 595 supports the following additional measurements via the measure and
concurrent measurement commands.
aM1! = Maximum Level / Pressure
aM2! = Minimum level / Pressure
aM3! = Maximum Temperature
aM4! = Minimum Temperature
The maximum and minimum values should be reset using the XMM command
as shown in Table 10.
Table 10
Resetting Maximums and Minimums
Command Response Comment
aXMM1! a1! Resets the maximum level to the current value
aXMM2! a2! Resets the minimum level to the current value
aXMM3! a3! Resets the maximum temperature to the current value
aXMM4! a4! Resets the minimum temperature to the current value
8. Maintenance
8.1 Self diagnostics
The 595 performs a significant amount of self-diagnostics upon reception of the
verify command, aV!. It is recommended that any system design should include a
periodic execution of the verify command. The response to a verification com-
mand includes an error code. Table 11 summarizes the possible error codes from
the verification command.
Table 11
Diagnostics
Error Code Description
0 No Error, unit is functioning normally
1 The temperature measurement is beyond the calibrated range
2 The pressure measurement is beyond the calibrated range
4 The nonvolatile memory has been incorrectly accessed
8 An analogue signal error exists
16 Reserved
32 The nonvolatile user data is in error
64 The nonvolatile calibration data is in error
128 RAM error
256 Watchdog error
Note: If an error code >3 is returned, record the value and contact the manufacturer