Instructions

UM-0085-B09 DT80 Range User Manual Page 367

• Ensure that there are no other Modbus master devices on the same serial network as the DT80. (For a TCP/IP

network multiple Modbus master devices can be present.)

• If transactions are failing intermittently, electrical noise may be disrupting the network. If this cannot be rectified

then it may help to use the RTn channel option to tell the DT80 to retry failed transactions a few times.

If the MODBUS channel is reliably returning values, but the values seem to be wrong, then check the following:

• Make sure you have specified the correct register number. Be careful of "off by one" problems, as some device

documentation specifies 0-based protocol addresses, rather than the 1-based register numbers used by the R

channel option.

• Has any required scaling factor or span been applied correctly? Double check the device documentation.

• For 32-bit integer or floating point quantities be sure to specify the correct data format option, e.g.

MBF if the

device returns an IEEE-754 floating point value, or

MBL for a long integer.

• For 32-bit quantities, it is also quite possible that your device may require the

MBR option as both "straight" and

"reversed" word ordering are widely used.