Bulletin D-57
Model 1430 Microtector®Electronic Point Gage
Installation and Operating Instructions
Model 1430 Microtector®Portable
Electronic Point Gage combines mod-
ern, solid-state integrated circuit electronics with a time-proven point gage
manometer to provide fast, accurate
pressure measurements.
SPECIFICATIONS AND FEATURES
• Accurate and repeatable to ± .00025
inches water column
• Pressure range: 0 - 2˝ w.c., positive,
negative, or differential pressures
• Non-toxic and inexpensive gage fluid
consists of distilled water mixed with
a small amount of fluorescein green
color concentrate
• Convenient, portable, lightweight
and self-contained, the unit requires
no external power connections and
is operated by a 1.5 volt penlight cell
• A.C. detector current eliminates
point plating, fouling and erosion
• Micrometers are manufactured in accordance with ASME B89.1.13-2001, and
are traceable to a standard at the National
Institute of Standards and Technology
*
*
Patent No. 3,726,142
• Three-point mounting, dual leveling
adjustment, and circular level vial
assure rapid setup
• Durablock precision-machined acrylic
plastic gage body
• Sensitive 0 - 50 microamp D.C. meter
acts as a detector and also indicates
battery and probe condition
• Heavy 2˝ thick steel base plate
provides steady mounting
• Top-quality glass epoxy circuit board
and solid-state, integrated circuit
electronics
• Electronic enclosure of tough, molded
styrene acrylonitrile provides maximum
protection to components yet allows
easy access to battery compartment
• Rugged sheet steel cover and carrying
case protects the entire unit when not
in use
• Accessories included are (2) 3-foot
lengths Tygon tubing, (2) 1/8˝ pipe
thread adapters and 3/4 oz. bottle of
fluorescein green color concentrate
with wetting agent
Maximum pressure: 100 psig with
optional pipe thread connections.
OFF
ON
LOW
PRESSURE
FLUID
LEVEL
Microtector®Gage
Precision Pressure Measurement
The Dwyer Microtector®combines the timeproven principles of the Hook Gage type
manometer and modern solid-state integrated circuit electronics. It provides an inexpensive means of achieving accuracy and
repeatability within ± .00025 inches water column throughout its 0 to 2 inches w.c. range.
It is truly a new standard in precision measuring devices.
Principles of Operation
A pressure to be measured is applied to the
manometer fluid which is displaced in each
leg of the manometer by an amount equal to
1/2 the applied pressure. A micrometer
mounted point is then lowered until it contacts
the manometer gage fluid. The instant of contact is detected by completion of a low-power
A.C. circuit. Current for this circuit is supplied
by a 1.5 volt penlight cell feeding two semiconductor amplifiers which act as a free-running multivibrator operating at a frequency of
approximately two kilohertz. Completion of
the A.C. circuit activates a bridge rectifier
which provides the signal for indication on a
sensitive (0 to 50 microamps) D.C. microammeter.
On indication of contact, the operator stops
lowering the point and reads the micrometer
which indicates one half the applied pressure.
By interpolating eight divisions (each being
.000125˝ w.c.) between .001 micrometer
graduations, a total accuracy of .00025 can
easily be achieved. The micrometer complies
with Federal Specification GGG-C-105A and
is traceable to a master at the NIST.
Locating and Opening
Stand the Microtector®and case on a firm flat
level surface. Remove cover by releasing the
latches and lifting it straight up. If it is necessary to move the gage without case, handle
only the base plate or clear acrylic block.
(CAUTION: Do not handle gage by grasping
meter-electronic package housing Item 7 on
drawing.)
2
Fluid Level
Level the gage by adjusting the two front leveling screws (Item 8 on drawing) until the bubble in the spirit level is centered in the small
circle. After leveling the gage, open both
rapid shut-off valve tube connectors (Items 2
and 5). Back off the micrometer (Item 4), if
necessary, to make sure that the point is not
immersed in the gage fluid. The fluid level in
the gage should now coincide with the mark
on the right hand bore (Item 6) plus or minus
approximately 1/32 inch. If the level of fluid is
too high, fluid can be removed with an eye
dropper pipette or carefully poured out of the
right connection (Item 5).
If the level is too low, remove the top left rapid
shut-off valve tube connector(Item 2) and add
distilled water pre-mixed with the proper
amount of Dwyer green concentrate. (See
maintenance instructions for proportions.
After correcting the fluid level, re-install the
rapid shut-off connectors and, with these in
the open position, re-level the Microtector
The gage is now ready to be zeroed.
Zeroing
Turn the Micrometer barrel (Item 4) until its
lower end just coincides with the zero mark
on the scale and the zero on the barrel scale
coincides with the vertical line on the internal
scale. Note that the internal scale is graduated every .025˝ from 0 to 1.00 inch and the
barrel scale is graduated in one thousandths
from 0 to .025˝. Turn the meter circuit switch
at the top of gage to the “on” position. While
holding the barrel at the zero position (and
with gage level), raise or lower the point by
turning the knurled knob (Item 3) until the
point is above, but near, the fluid.
Check to be sure that the meter registers
zero. Watch the meter, hold the barrel, and
lower the point slowly by turning the top
knurled knob. As the knob is turned, the
point will contact the fluid and the meter
pointer will move from zero to some upscale
position.
After making contact, turn the point out of the
fluid by turning the micrometer barrel counter clockwise to a reading of .010 or more.
Again, watch the meter and, this time, lower
the point by turning the micrometer barrel.
The point position where the meter pointer
begins to move up scale is the zero position.
This position should correspond to the zero
reading on the micrometer. Adjust the point in
relation to the micrometer barrel by turning
the top knob while holding the barrel steady.
Repeat lowering the point, watching the
meter for contact, and adjusting the point
until the zero position and zero reading exactly coincide. The gage is now zeroed and
should not be moved.
An alternative method of zeroing and reading
can be used wherein, instead of zeroing the
gage completely, a zero correction reading is
taken and recorded, then subtracted from the
final reading. Comparable results can be
obtained with either method.
®
.
Positive Pressure Measurement
With the fluid at its proper level, a pressure of
2.0˝ water column maximum can be measured. Positive pressure should be applied to
the top left connection (Item 2) with the
micrometer zeroed as described above. This
will permit a simple direct reading to be taken.
After an unknown pressure has been applied
at the top left connection, the fluid level will
drop in the left bore and rise over the point in
the right bore. Note that the indicating meter
point has moved upscale because the point is
immersed in the fluid. Turn the micrometer
counter-clockwise until the point leaves the
fluid as indicated by the meter pointer dropping to zero on its scale. Then slowly turn the
micrometer down until its point just touches
the fluid surface, causing movement of the
meter pointer. Withdraw the point and repeat
several times, noting each time the micrometer reading where the meter pointer begins.
The average of these readings multiplied by
two is the pressure applied to the gage. (Avg.
reading x 2 = pressure applied in inches w.c.
The degree of uncertainty for the operator is
indicated by the difference in these readings.
3
When the readings are complete, the pressure should be removed and the zero setting
of Microtector
®
rechecked. Any change in the
zero position will indicate inaccurate readings.
Should this happen, the zero-set and pressure measurement procedure should be
repeated.
Negative Pressure
or Vacuum Measurement
Zero the gage. Connect the source of vacuum or negative pressure to the right-side
gage connection (Item 5) and proceed as
described under Positive Pressure
Measurement section. Remember that the
pressure measured in this way is negative.
Differential Pressure Measurement
Differential pressures may be measured by
connecting the higher (more positive) pressure to the left connection (Item 2) and the
lower pressure to the right connection (Item
5).
Storage
Turn meter circuit switch to “off” position and
withdraw the point well clear of fluid (by turning micrometer clockwise) when gage is not in
use. This will conserve the batteries and minimize build-up of oxides, etc., on the point.
Keep the unit covered and in an area free of
strong solvent fumes.
(2) If the meter operation continues to be
sluggish, replace the size AA, 1.5 volt battery.
(Replace the battery at least once a year to
avoid deterioration of battery and damage to
gage. Leakproof alkaline battery is recommended.)
To replace the battery, remove center screw
(Item 10) located in the back of the electronic
enclosure. Cover (Item 9) will come off,
exposing the battery. Pull the old battery out
and push a new battery into the battery holder with the positive (center) terminal to the
right (to the end marked with + on the holder).
If the fluid becomes contaminated and
requires replacement: empty old fluid from
gage; flush out with clear water and replace
with distilled water and Dwyer A126 fluorescein green color concentrate mixed with 3/4
oz. concentrate to each quart of water.
CAUTION:
1. Do not substitute other gage fluids, as
proper gage operation depends on use of the
specified gage fluid to provide proper surface
tension, wetting ability and electrolyte capability with unity specific gravity.
If the gage bore is very dirty, a mild soap solution may be used to aid in cleaning prior to
flushing with clear water.
Maintenance
When the meter reading becomes reduced or
the pointer movement gets sluggish (with the
circuit on and the point in fluid), the following
should be done:
2. Do not clean with liquid soaps, special solvent, de-greasers, aromatic hydrocarbons,
etc. Such cleaners and solvents may contain
chlorine, fluorine, acetone and related compounds that will permanently damage the
gage and prevent proper operation.
(1) Remove the point (by unscrewing) and
clean the tip lightly using fine crocus cloth.
Wipe off all grit and dirt with a clean rag;
reassemble and recheck meter operation.
©Copyright 2005 Dwyer Instruments, Inc Printed in U.S.A. 10/05 FR# 38-440190-00 Rev. 7
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