Chemglass CG-4600-01 - Manual (Page 9)

9
3.6 Using the Regulator for Vacuum Distillations. This version of the vacuum regulator is intended for
medium accuracy vacuum applications, such as rotary evaporators. We say medium accuracy applications
because the regulator usually regulates pressure from ± 0.5 to ± 2 torr (as opposed to a high accuracy
regulator that controls pressure to better than ±0.1 torr). Some vacuum distillations are not affected by
changes in pressure of ± 0.5 torr, but many are. This regulator is not recommended for small, laboratory
scale vacuum distillations. Having said that, we at J-KEM know you’re going to try it anyway, so let us
help you set the distillation up to deliver the best performance possible.
Points to follow:
1. Use a precision needle valve (available from J-KEM) between the vacuum pump and the vacuum
regulator. Adjust the opening of the valve after reaching the set point pressure of the distillation to
minimize fluctuations.
2. Use a cold trap between the distillation set up and the vacuum regulator.
3. The pressure reading begins to lose linearity below 12 torr. The pressure reading will be consistent, but
its absolute value may be off by as much as 2 torr.
4. Good luck and give us a call if you need additional assistance.
[NOTE: J-KEM does manufacture a precision computer controlled high accuracy vacuum controller, our
DVR-1000]
3.7 Correcting Offset in the Displayed Pressure. A small amount of error can develop in the displayed
pressure (≈ 2 torr) of the vacuum regulator. This is due to the wide pressure range of the transducer used and
accuracy better than this is usually not possible. For display errors larger than 2mm, the controller can be
calibrated using the procedure below (For users experienced with J-KEM’s meter, do not correct pressure
using the “
ZEro” function. This introduces an error, not a correction). Before beginning this procedure you
will need to know the correct barometric pressure inside your lab.
This procedure should only be performed by a qualified electrician.
1. Remove the controller’s cover.
2. Plug the OUTLET port of the regulator and set
the regulator selection switch to the FULL
VACUUM position.
3. Let the controller warm up for 10 minutes.
4. Connect a vacuum pump to the INLET port, turn
it on and let it evacuate the controller to as close
to 0 torr as possible. Measure the pressure in the
system using a manometer. The regulator must
be evacuated to as close to 0 torr as possible
before the adjustment in step 5 is performed.
5. Adjust the “Zero” pot until the reading on the
meter matches the actual pressure.
6. Turn the vacuum pump off and unplug the
OUTLET port. Adjust the “Span” pot until the
meter reads the actual barometric pressure in the
lab.
7. Turn the controller off and replace the cover.