The load cell is calibrated via the Zenosoft user menus which are accessed via the laptop computer using the Hyperterm program which is supplied with Microsoft Windows operating systems.  Click here for Hyperterm configuration instructions.

7.1 From the user menu, at the ‘>’ prompt, type   t<enter>.   This will display a test menu similar to the one shown below:

7.2 At the ‘>’ prompt, type   c1<enter>.   This is a request to calibrate sensor number one. This will display the sensor name, the current ‘A’ conversion coefficient, and a prompt to enter a new ‘A’ conversion coefficient.

7.3 At the prompt to enter a new ‘A’ conversion coefficient, enter 0 (zero) <enter>.

7.4 Similarly, the screen will display with the current ‘B’ coefficient and prompt for a new value. For this value type 1000<enter>:

7.5 Finally, the screen will show the current ‘C’ coefficient and prompt for a new value. For this value type 0<enter>:

After entering the new ‘C’ coefficient value, the screen will return to the test menu.

7.6 Start with an empty bucket. Lower the shipping bolt so that there is a visible gap (~ 1/4 inch) between the end of the bolt and the front support. Verify that the plunger is touching the load cell ball bearing and that the weight of the empty bucket assembly is on the load cell.

7.7 At the test menu prompt type   s1,1<enter>.   This will result in the output of sensor measurements for the first sensor (precipitation weighing sensor) every second:

7.8 The displayed value should change every six seconds (six readings) or so. Allow this to run for at least 30 seconds for the readings to stabilize. Then, as the numbers scroll by, record 10 different values and average them. Label the averaged value, B1, for use later.

7.9 When done, press   <enter>   on the laptop to halt the update. The test menu will return

7.10 Place exactly 15 inches of equivalent weight in the bucket. If using the F&P calibration weight set (D111-TE500), add the three large weights to the bucket. Be careful not to drop the weights. You will not damage the load cell, but you may bend the flexures.

7.11 At the test menu prompt type   s1,1<enter>.   Allow time for the readings to stabilize, then as the readings scroll by, record 10 different values and average them. Label the averaged value, B2, for later use.

7.12 When done, press <enter> to halt the update. The test menu will return.

7.13 Calculate new gain coefficient B with B = 15000/(B2-B1).

[This equation represents: (15" x gain) / (full weight - empty weight)]

Type c1 at the prompt to enter the new gain coefficient B. Leave A and C at zero by pressing <enter> at both prompts. Enter the calculated B value for coefficient B.

The test menu will return.

7.14 Adjust the precipitation gauge so that the weight of the empty bucket assembly is on the load cell.

7.15 At the test menu prompt type   ‘s1,1’ followed by enter.   Record 10 different values and average them. Label this value as C3.

7.16 When done, press <enter> to halt the update. The test menu will return.

7.17 Calculate new coefficient C with C = -C3.

Type   c1   at the prompt to enter new calibration. Enter C value for coefficient C. Leave A and B as is by pressing   <enter>  for each.

The test menu will return.

7.18 With the plunger touching the load cell ball bearing and the weight of the bucket assembly on the load cell, place the equivalent weight of 15 inches of precipitation into the weighing bucket. (Add the three large weights of D111-TE500.)

7.19 At the test menu prompt type   ‘s1,1’ and <enter>.   Verify that these values are 15.0 ± 0.1 inches. Press   <enter>   when done to stop the scrolling data and return to the test menu. If not within the above range, redo the calibration from step 7.3

7.20 While still at the test menu, type   u<enter>   for the user menu and then type   c<enter>   to enter the communications menu.

7.21 Type e<enter> to save calibration values to EEPROM. The display should appear as below and then return to the communications menu.

7.22 Type q<enter> to quit the Zenosoft menus.