
PT12 INSTRUCTIONS
Seametrics • 253.872.0284 Page 10 seametrics.com
OPERATION/MODBUS RTU
Calibration and Conversion Constants
The data is returned as a 32-bit IEEE oating-point value,
high word rst, also referred to as big-endian, oat inverse,
or Float AB CD.
Field calibration values and units conversion values can be
set by the user. If set, these values will be applied to the
readings before values are returned.
Zero-
Based
One-
Based
+40,001 Description
200-01 201-02 40201-02 Factory Calibration* - Pressure Scale
202-03 203-04 40203-04 Factory Calibration* - Pressure Linearization 1
204-05 205-06 40205-06 Factory Calibration* - Pressure Linearization 2
206-07 207-08 40207-08 Factory Calibration* - Pressure Slope 0
208-09 209-10 40209-10 Factory Calibration* - Pressure Slope 1
210-11 211-12 40211-12 Factory Calibration* - Pressure Slope 2
212-13 213-14 40213-14 Factory Calibration* - Pressure Oset 0
214-15 215-16 40215-16 Factory Calibration* - Pressure Oset 1
216-17 217-18 40217-18 Factory Calibration* - Pressure Oset 2
218-19 219-20 40219-20 Field Calibration - Pressure Slope
220-21 221-22 40221-22 Field Calibration - Pressure Oset
222-23 223-24 40223-24 Field Calibration - Temperature Slope
224-25 225-26 40225-26 Field Calibration - Temperature Oset
226-27 227-28 40227-28 Factory Calibration* - Temperature Alpha
228-29 229-30 40229-30 Factory Calibration* - Temperature Oset
230-31 231-32 40231-32 Factory Calibration* - Tempearture Slope
232-33 233-34 40233-34 Pressure Units - Conversion Slope
234-35 235-36 40235-36 Pressure Units - Conversion Oset
236-37 237-38 40237-38 Temperature Units - Conversion Slope
238-39 239-40 40239-40 Temperature Units - Conversion Oset
* Factory calibration values are set at the factory.
Writing to Factory Calibration
registers will void calibration!
Zero-
Based
One-
Based
+40,001 Description
300=n 301=n 40301=n Set averaging: This enables sensor for n
seconds. Each second, the statistical data
registers will be updated to contain new
averages, max and min. At the completion of n
seconds, the nal statistical values will be left in
the registers, and the sensor will be put to sleep.
n = 0..10,800. If n = 0, the sensor is put to sleep,
and the statistical data values are not updated.
400=a 401=a 40401=a Set sensor address = a (Write Only)
500=b 501=b 40501=b Set baud rate = b (Write only)
0=38400, 1=19200 (default), 2=9600, 3=4800,
4=2400, 5=1200
600=w 601=w 40601=w Set auto-enable. Causes sensor to be enabled
automatically for w seconds after a read of any
parameter data register. W=0 disables auto-
enable. (This is normally set to 10 seconds at the
factory.) For lowest power usage, set this to zero.
For fastest readings while still retaining as much
power savings as possible, set slightly longer
than your read frequency. See section below
for information on how this setting aects your
readings.
700=L 701=L 40701=L Set serial number. L= unsigned longword value
0x0000000 .. 0xFFFFFFF (0 .. 4,294,967,295)
800 801 40801 Read sensor rmware revision. Word MSB =
Major revision, LSB = minor revision.
E.g., 0013 = revision 0.13
Sensor Conguration/Control
Readings and the Auto-Enable Setting
When a reading is requested, four things happen:
• The sensor wakes up.
• The current value in the register is returned.
• The sensor turns on the analog portion, begins
sampling, and begins putting the new values in the
registers.
• If auto-enable is set to a positive value w, the sensor
stays awake for w seconds, sampling and moving
values into the registers all the while, and then goes
to sleep.
• If auto-enable is set to zero, the sensor immediately
goes to sleep after putting the reading in the
register.
If your read frequency is less than the auto-enable value,
the sensor will stay on continuously, and your readings will
always be fresh, with the exception of the very rst reading.
If your read frequency is greater than the auto-enable
value, the following reading sequence is recommended:
1. Request a reading. This begins the wakeup process
on the sensor and returns the value currently in the
register, which will be old data. Throw this value
away.
2. Wait one second, then take another reading. This
reading will have fresh data. Record this reading.