DigiVac VAPOR User manual
YOU MUST READ THIS MANUAL BEFORE USE
2
Table of Contents
Calibration Procedure.....................................................................................................................................6
Sensor and Plumbing......................................................................................................................................7
Maintenance ....................................................................................................................................................7
Notes on calibration........................................................................................................................................7
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The DigiVac Vapor Pressure Controller (VPC), is a rugged, modern vacuum measurement and
control instrument designed to make vacuum measurement and regulation easy through the
use of a simple LED readout and large tactile buttons. Electronically, it is a highly accurate
digital vacuum gauge utilizing field-proven isolated vacuum sensor technology coupled with
reliable valve and plumbing parts. This regulator was specifically designed for chemistry
distillations that can be aided by precise pressure control. The VPC facilitates separating
chemicals that have vapor pressures as close as 10 Torr to one another. It can also be used
to prevent bumping by gradually changing the pressure. The VPC can also help save your
pump, widen the choices of pumps you can use for low temperature distillation, and keep
vacuum pump oil out of your system.
●All metal case protects flow components & electronics
●Field-proven isolated vacuum sensing technology to avoid sensor failure
●775i sensor designed to be used in chemistry and industrial environments
●Calibrated at the factory against a NIST standard
●Very simple electronics
●Easy to understand
•Larger diameter valve than commonly available –makes pump downs faster
•Fine Grained Vacuum Control
•Simultaneous display of both current vacuum and set point
•Direct one touch set point setting
•Remote control via USB
•Replacement Sensor –SEN-775i-NPT-OEM
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For the VPC distillation vacuum regulator.
Unpack and Confirm: Verify you’ve received everything you ordered
The vacuum instrument contains the following components:
1. Vacuum distillation regulator with an international power supply
2. Quick Start guide or (this) User Manual
Easy to use steps:
1. Plug in the system to wall power and make sure LEDs light up
2. Mount VPC in desired location
3. Connect a hose from the vacuum pump to the port on the VPC labeled “Vacuum
Pump”
4. Connect a hose from the system to the port on the VPC labeled “System to be
controlled”
5. Use up and down arrows to set the target vacuum
pressure
6. Read and control vacuum!
Beyond the Quick Start installation instructions, care should
be taken to insure clean leak free connections using high quality
components. Below are some best practices for installation:
•Use high quality chemically resistant hose that won’t breakdown and degrade with your
process
•Use hose clamps or another way to minimize leakage at vacuum interfaces
•Use Teflon tape on all NPT fittings. Consult our guide on best practices for NPT
connections.
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The only required connections for operation are power, vacuum pump and system. A USB
port also exists for the purpose of connecting to the VPC remotely to enable remote control
and logging.
This VPC is equipped with a set point that defines the vacuum pressure that will be achieved.
To set the set point:
Step 1. Note the current set point indicated by the Green LED display.
Step 2. Press up or down to set the new set point. Note once the up or down button is
depressed, the unit will immediately control to the new set point. Also note that the up and
down arrows are “typomatic” such that the numbers will move faster the longer they are
pressed.
The unit can be communicated with remotely using simple ASCII commands. Below is a
summary of those commands:
•S=320 set current setpoint to 320 Torr
•S? queries current set point
•Vac? queries current vacuum level
•M? get mode setting
•M=A set mode to automatic, where current vacuum reading and set point are sent
over the wire at a rate of once per second
•M=M sets mode to manual, where the unit will wait for a query
•U? gets the current units
•U=0 sets the units to Torr
•U=1 sets the units to mbar
•U=2 sets the units to kPa
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The VPC family of products can be calibrated in the field provided that an accurate vacuum
instrument standard exists. Typically, that instrument standard should be 4x as accurate, or
at the very least much more accurate than the VPC. The standard should resolve to better
than +/- 0.25 Torr.
Calibration Procedure
1. Plug in A/C adapter, connect cable to vacuum sensor. Maintain system at 2 Torr +/-
0.25 Torr. Turn “Vac” pot so the vacuum on the VPC reads 2 Torr
2. Raise pressure to 760 Torr. Adjust “SPAN” so VPC indicates 760 Torr
Here are a few trouble shooting steps:
Observation
Possible Causes
System does not light up
Verify the system is plugged in, and all the cords
are tight
System takes too long between set points
•Take VPC out of the configuration
•Time how long it takes for system without
VPC to get from the first vacuum level to
the second vacuum level
•Re-install the VPC and run same test
•Rerun the same test with a tuned orifice of
0.150”
•If the last 2 test are close, that means the
VPC is performing as it should. If the last 2
tests are different, it means the VPC is not
performing optimally. Please consult your
vendor for technical assistance.
My readings are erratic
Check reading with another gauge to see if the
readings are indeed erratic. If the other gauge
does not show erratic readings, consult your
vendor.
When I turn on my unit and turn on my vacuum
pump, the vacuum reading doesn’t go down.
Verify the switch on the right is in the “regulate”
setting, and the vacuum pump is running.
My VPC is really noisy
The VPC valve is a bit noisy, but more of a finger
tapping loudness. If you hear a loud metallic
sound, then something is wrong. Consult your
vendor.
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Sensor and Plumbing
In many cases, a sensor may become fouled with oil or other foreign matter. It is often
possible to restore the functionality of contaminated probes with cleaning. If the contaminant
is known, the VPC plumbing should be filled with a fluid that is known to be a solvent to that
contaminant. As an example, ether is often effective in removing residues of some oils.
Commercial carburetor cleaners are very powerful solvents and are highly effective against
some contaminants.
After cleaning with solvents, the plumbing should be completely dried or flushed with a volatile
solvent to assure that it is dry prior to reinstalling it.
If this is not done, contamination of the
system may result.
Maintenance
Your vacuum instrument should give you many years of trouble-free service. There are no
regularly scheduled maintenance intervals. If consistent accuracy is required, it is
recommended that the VPC and power supply be returned for a yearly calibration check.
Notes on calibration
There is inherent drift in all sensors including the DigiVac 775i piezo resistive sensor. Drift is
specified in the datasheet, but the specification is typically a worst case scenario as drift is not
easily predicted and depends on operating environment. Depending on your accuracy
requirements, it makes sense to set up a calibration interval to obtain as found data, and get a
fresh calibration. Having this information will allow you to determine the optimal calibration
interval. The accepted interval is 1 year, but depends on what accuracy you require and what
you’ve defined in your standard operating procedures.
Note the sensors have excellent accuracy by themselves. Additional accuracy is gained by
calibrating the sensor controller (the thing with the display and cable coming out of it) to the
sensor. The sensor itself is cannot be calibrated, but the sensor-controller pair is. See our
blog on sensor interchangeability effects on accuracy for the Bullseye Precision Gauge Piezo
for more information.
Note that the 775i sensors accuracy applies to any type of measurable gases. Readings will
be correct regardless of the type of gas you are trying to measure.
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Instrument Repeatable Accuracy
Range
Accuracy
Accuracy:
+/- 2 Torr
Control band
+/- 2 Torr
Vacuum Reference:
Absolute
Sensor:
SEN-775i-NPT-OEM
Resolution:
+/- 0.1 Torr
Units:
Torr, mbar
Accuracy:
+/- 2 Torr
Range
1-775 Torr
Control band
+/- 2 Torr
Mount
Desktop or laboratory pole mount
Display
0.56 inch Purple LED for Pressure, 0.36 inch Green LED
for SP
Product Dimensions
5"w x 6.25"d x 4"h
Power
110 Volt standard wall receptacle
Compliance
CE compliant
Wetted Materials
316 SS, 304 SS, Nickel, chemically resistant rubber
Effective Orifice
0.150 in
Connectivity
USB
Vacuum Interface
1/8" FNPT (if you remove the nipple), 1/8"MNPT, 1/4"
ID hose with a barb, 3/8”ID hose fits over the nipple
LED Heights
.56”
.35”
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This instrument and many similar instruments are calibrated in microns or "milliTorr." It is
appropriate to discuss what microns are and to relate microns to other measures of
pressure and vacuum. Microns are not really a measure of vacuum at all, but rather of
absolute pressure.
The pressure of the atmosphere is 14.696 or approximately 14.7 pounds per square inch at
sea level. One TORR is an absolute pressure of one millimeter of mercury. A milliTorr is equal
to one thousandth of a TORR. A MICRON is the same as a milliTorr.
This pressure is due to the weight of all of the air in the earth's atmosphere above any
particular square inch. This 14.696 PSI is equivalent to the pressure produced by a mercury
column of approximately 29.92 inches high or .76 meters (~ 3/4 of a yard) or 760
millimeters of mercury.
Atmospheric pressure varies greatly with altitude. It decreases approximately 1 inch of
mercury per thousand feet of altitude. It also varies widely with local weather conditions.
(Variations of one half inch in a single day are common.) The word “vacuum”means pressure
lower than atmosphere or "suction." However, in describing negative pressure, the
atmosphere is only a satisfactory reference if we are dealing with values of vacuum down to
about 27 inches of mercury. Below that, it is much more useful to talk in terms of absolute
pressure, starting from absolute zero. The Vacuum Gauge does just this.
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