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Click Here to Learn More!When communicating with the Hardy units, when the data from the unit is transferred it is being transferred in 16 bit words. The PLC system reading this data will interpret the upper bit of the data as a sign bit. So, once the data reaches a value of 32768, this upper bit is being set and the PLC thinks it is a negative number.
There are various ways around this problem depending on which model of Hardy Instrument you are using.
In the HI 2151 and HI 2100 series units using RIO communications you can do a bit shift that will reduce the value being transferred. Each bit shift will reduce the value by 1/2 and you would need to multiply the value by the appropriate value to get the real value.
In some PLC's you can copy the values into a DINT location (32 bits) that will not interpret the 16th bit as a sign bit.
Some units, like the HI 1746WS and HI 200DNWM, have a multiplier that may be reduced to lower the value being sent. Sometimes the user is trying to get more resolution and runs into this issue. Reducing the resolution reduces the value. On units that use a multiplier, you can reduce the multiplier, causing the resolution to change. Example: If the multiplier is 100 and you are running into problems at 327.67 lbs, change the multiplier to 10 and you would then be able to read up to 3276.7 lbs before you have the same problem, but your resolution is now less than before.
You can also put the value through an Integer to Float conversion that will correct the misinterpretation of the upper bit. You can find an example of an integer to float conversion routine in the attached tech note "Integer to Float conversion".
Please review the attached Tech Note titled "20 BIT DATA IN 16 BIT INTEGER LOCATIONS" for additional information.
