such meters, it is generally best to
operate the OMNI-AMP Amplifier as a
constant voltage device. With OMNI-AMP
II Amplifier, this is achieved by placing
the mode switch in the volt/volt position.
In the case of the OMNI-AMP I Amplifier,
it is set for constant voltage mode when it
leaves the factory. Certain pyrometers
are low impedance devices having a
circuit resistance of only a few ohms. In
such cases, the OMNI-AMP Amplifier
should be operated as a constant current
device. With OMNI-AMP II Amplifier,
simply place the mode switch in the
MA/VOLT position. With OMNI-AMP I
Amplifier, it is necessary to remove the
cover plate and throw the small internal
switch to the position suggested in the
instructions on the side of the OMNI-AMP
Amplifier.
Your OMNI-AMP Amplifier has been
designed to have an extremely low dc
drift as a function of time and
temperature. However, if your application
is to amplify signals which are in the
region below five millivolts, you will
enhance the already low drift
characteristics of this instrument by first
allowing a 15-minute warm up period,
and then by maintaining the temperature
of the OMNI-AMP Amplifier as constant
as possible.
Note: OMNI-AMP IIB Amplifier with
reference junction. This unit contains a
selfcompensating electrical bridge
network incorporating a temperature
sensitive resistance element that is
powered by a 3.6V lithium battery to
ensure a reference junction at 0°C or
32°F. Be certain that the thermocouple
used in conjunction with
OMNI-AMP IIB Amplifier is of the
calibration designated on the input
connector.
Important considerations when using
your OMNI-AMP Millivolt Amplifier
Before using an OMEGA
®
OMNI-AMP
millivolt amplifier, please check your
recorder, meter or oscilloscope for the
following:
1. If you are using an oscilloscope and it
has a sensitivity of 1 millivolt/
centimeter or better (500 microvolts/
centimeter, 100 microvolts/centimeter),
then OMNI-AMP Amplifier SHOULD
NOT BE USED as it will not amplify
your thermocouple EMF without
excessive noise. If your oscilloscope
has a sensitivity of less than 1 millivolt/
centimeter (500 millivolts/centimeter, 1
volt/centimeter, etc.), then your OMNI-
AMP Amplifier will be quite helpful in
boosting the oscilloscope sensitivity.
Keep in mind that the lower the gain or
sensitivity of the oscilloscope, the
higher the useful gain of your OMNI-
AMP Amplifier.
2. If you are using a meter which has a
full scale sensitivity of 10 millivolts or
better (500 microvolts full scale, 100
microvolts full scale, etc,), then your
OMNI-AMP Amplifier SHOULD NOT
BE USED as it will not be able to
amplify the EMF without excessive
noise. If your readout meter has a
sensitivity of less than 10 millivolts full
scale; i.e,1 volt full scale, then your
OMNI-AMP Amplifier will be very
helpful in boosting the meter’s
sensitivity. Keep in mind that the lower
the gain or sensitivity of the readout
meter, the higher the useful gain of
your OMNI-AMP Amplifier.
3. If you are working with an oscillograph
recorder and it has a sensitivity of 1
millivolt/centimeter or better, then the
OMNI-AMP Amplifier should not be
used as it will not be able to amplify the
EMF without excessive noise. If your
oscillograph recorder has a sensitivity
of less than 1 millivolt/ centimeter, then
your OMNI-AMP Amplifier will be very
helpful in boosting the oscillograph
recorder’s sensitivity considerably. As
with meters and oscilloscopes, keep in
mind that the lower the gain or
sensitivity of the oscillograph recorder,
the higher the useful gain of your
OMNI-AMP Amplifier.
4. The OMNI-AMP Millivolt Amplifier is
NOT RECOMMENDED for use with
digital readout meters unless the
maximum sensitivity is
1 millivolt. In any event, if a decision is
made to use a OMNI-AMP Amplifier
with a digital readout meter, the
maximum sensitivity that can be
achieved with a meter and OMNI-AMP
Amplifier combination is 100
microvolts.
Please read the operating instructions
which are on the side of the OMNI-
AMP I Amplifier and on the bottom of
OMNI-AMP II Amplifier before using
the instrument.
