Rockwell-automation 1771-IR , D17716.5.76 RTD INPUT MODULE Manual de usuario descargar pdf (Pagina 40)

Module Calibration

Chapter 7

77

is, you want to subtract 47 counts from your input data. The lower byte

remains 00 during offset calibration.

5. Repeat above steps for channels 2 through 6 respectively.

6. Apply the values by sending a BTW to the module.

Gain Calibration

1. Connect the 402.00, .01% resistors to the swing arm as shown in

Figure 7.2.

2. Place the module in platinum ohm mode. This provides 30 mohm

resolution display.

3. Examine word 3 of the read block transfer data file. It should be around

13400 decimal. Your actual value will be a percentage of 13400.

For example, if the data in word 3 is 13408, then:

(13400–13408)/134000 = –0.000597.

Your actual data value differs from the theoretical value (at 402.0 ohms

input resistance) by –0.000597, or –0.0597%.

You can compensate for this error by entering the percentage difference in

binary coded fraction form. Table 7.D lists the value for bits 7–0.

Table 7.D

Value

for Bits 7 through 0

Bit Value

Bit 07 Sign bit

Bit 06 = 0.0976562%

Bit 05 = 0.0488281%

Bit 04 = 0.024414%

Bit 03 = 0.012207%

Bit 02 = 0.00610351%

Bit 01 = 0.00305175%

Bit 00 = 0.00152587%

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 67 68

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Rockwell-automation 1771-IR , D17716.5.76 RTD INPUT MODULE Manual de usuario Pagina 40