Scales

In addition to our various regular scales that we use for weighing out dry materials, we also have two scales that we use as part of DAQ:

Arlyn Model 3200, 0-1000 lb, 4-20 mA output, used in Patient Care Vault to monitor dewar weight

Arlyn Model 620F, 0-150 lb, 4-20 mA output, used in DAQ Wiring Box for Perfusion Monitor Reservoir Level.

We have made the following changes to the settings on each scale:

1. Setup Menu, System, Startup Parameters, Ready=Disabled. Staff should not have to push any buttons to get it working after power loss.

2. Setup Menu, System, Startup Parameters, Splash=Disabled. Staff should not have to push any buttons to get it working after power loss.

On the larger scale in the Patient Care Vault, we also made these additional changes:

3. Setup Menu, System, Startup Parameters, ZroKey=Locked. Prevents staff from accidentally resetting zero. Manual says that Zero and Print buttons together will zero in this mode, but they don't. To zero, change this setting, then change it again after zero.

4. Setup Menu, Platform Setups, Auto Zero = None. Prevents a reset of zero if power is lost.

Using the Scale

Generally just don't touch the buttons, as there is no need. If net or tare is showing on the display, press the Net/Gross button to clear out the tare and return to Gross mode. Net/Tare cannot be used, since it would not match the 4-20 mA output. Only Gross is used.

On the larger scale in the Patient Care Vault, the value showing on the display and on the computer normally differ by one or two pounds. This is ok, and is just natural drift. The only way to fix it would be to roll the dewar off the scale, zero as described above, and then roll it back on. It's not worth the effort, and the discrepancy is not significant enough to cause any problems.

After a power failure, the weight output to the computer might not register. A power cycle might help. Setting the tare might help (not sure why).

Electrical Connections

The 4-20 mA output is on two wires. We connect these to a 3.5mm mini headphone plug, mono not stereo.

Wire Color	Polarity	Plug
Red	+	tip
Black	-	sleeve

The headphone plug then plugs into the back panel of the wiring box, and also allows extension cords.

In the Patient Care Vault, we wire directly into the NI 9203 module as described on that page.