Watlow Series PD - Manual (Page 64)

W a t l o w S e r i e s P D
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C h a p t e r 9 D e v i c e C o n f i g . T a b l e s
9
Parameter Tables
These tables contain detailed information for the all of the parameters contained in Series PD controller. The
tables consist of six fields for each parameter listed. These are:
• Parameter Name and Description - name of the parameter and a brief description. Some functions may
have more detailed information available in the Features chapters
• Web Page - web page the parameter appears on.
• Settings - blank column to allow you to document your Series PD settings.
• Range - numeric range or selection choices.
• Default - factory default values.
• Modbus - Modbus register numbers, the read/write status and the scaling factor of the Modbus value.
The parameters are grouped together by function and are in the order that they appear on the web pages. Use
the search function to find a specific parameter.
Modbus
Read/Write Status - Some parameters list the read/write status only, no Modbus register numbers. These pa-
rameters are available through the web pages only.
Modbus Registers - Some parameter values are four byte integers and require two Modbus registers. The low
register number contains the two higher bytes and the high register number contains the two lower bytes.
To read 32-bit values:
The process value of the Series PD is contained in two registers. For example, register 31 contains the two high-
er bytes while register 32 contains the two lower bytes. The 16-bit value returned from register 31 is multiplied by
65535 and added to register 32 when working in decimal format. To place the decimal point, divide the results by
1000.
To write 32-bit values:
The setpoint value of the Series PD is contained in two registers. For example, register 76 contains the two
higher bytes, while register 77 contains the two lower bytes. The reverse of a read has to be performed. To write a
setpoint of 1250 degrees (which is really 1250.000) multiply the setpoint value (SP) by 1000. Add 65536 to negative
numbers. This produces the setpoint (SP) we want to send. To determine the most significant word (MSW), divide
the SP by 2
16 or 65536. To determine the least significant word (LSW), subtract from the SP the result of multiply-
ing the MSW by 2 16 .
SP = 1250 * 1000 = 1250000
MSW = 1250000 / 2^16 = 19
LSW = 1250000 - (19 * 2^16) = 4816
Scaling Factor - Multiplier or divisor for the parameter value.
Decimal Precision - Decimal precision is implied at three decimal places for integer values unless otherwise
noted.
All values used by the Series PD are integer values. Go to http://www.modbus.org for detailed information on the
Modbus TCP protocol.