Teledyne NV-100 User Manual

HASTINGS VACUUM GAUGES

MODEL NV-100

TELEDYNE BROWN ENGINEERING

HASTINGS INSTRUMENTS

P.O.BOX 1436

HAMPTON, VIRGINIA 23661 U.S.A.

TELEPHONE [phone]

FAX [phone]

TWX [phone]

EASYLINK: 62300280

© May 1994

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Hastings Instruments reserves the right to change or modify the design of its equipment without any
obligation to provide notification of change or intent to change.

103A - PAGE 2

GENERAL

The Hastings Model NV-100 Vacuum Gauge is a complete self contained instrument with all circuits mounted on the
rear of the meter case. A remote type DV-100 gauge tube is used as the pressure sensor. The instrument measures
pressures over the range of 0.1 to 100 Torr utilizing the well known Hastings directly heated thermopile. Unlike other
Hastings gauges, this instrument operates in a constant temperature mode rather than constant applied voltage. The
changes in power to create a constant temperature rise above ambient are measured by the indicating meter as a
function of pressure. Corrections for gasses of differing thermal conductivities are necessary as in all thermal
conductivity type vacuum gauges.

INSTALLATION

The instrument is factory calibrated and ready for use when received. All that is necessary to place the gauge in
operation is to install the gauge tube into the system, plug in the gauge tube cable, and connect the power cord to
the AC line. Gauge tubes should be installed with the open end pointing downward so as to be self draining. On
dusty or dirty systems, a Hastings particle drop-out (protective) trap is recommended (see Product Bulletin #352).

OPERATION

The gauge is in operation once connected to the gauge tube and power. An initial check of the mechanical meter zero
may be necessary upon receipt. To do this, unplug the power cord and set (if necessary) the meter mechanical zero
adjustment the front of the meter to read "ATM". On the rear of the instrument are two calibration adjustments, they
should be correct as received. An occasional check of the ATM adjustment may be desirable. Also, anytime a new
gauge tube is replaced it is desirable to reset the ATM adjustment.

To do this, expose the tube to atmospheric pressure after the gauge is fully warmed up (about 30 minutes) and
adjust the trim potentiometer marked ATM until the needle reads ATM. Use of a trim potentiometer tuning tool will
facilitate this adjustment.

NOTE: When turned off, the meter needle rests at the right side of the meter (ATM mark).

When no tube is plugged in, the instrument reads off the scale below zero. If a broken gauge tube is plugged in it
will read off scale above ATM. Replace with a new gauge tube.

The circuit has a protective shut-down circuit. This shuts down the electronics whenever a gauge tube is not plugged
into the socket. This is to prevent burning out gauge tubes by application of excessive power surges when plugging
in or unplugging gauge tubes. A delay circuit applies power gently when connected. Pins 1 and 2 of the gauge tube
activate the circuit and act as the interlock switch. Thus the instrument will not operate unless the correct gauge tube
is used. Troubleshooting the circuit on a bench cannot be accomplished unless these two pins are jumpered at the
gauge tube socket, or a DV-100 gauge tube is plugged into the socket.

TROUBLE SHOOTING

If troubles develop, always try a new gauge tube before suspecting other problems. To check gauge tubes for
continuity of thermocouples, first make sure that the gauge tube is at atmospheric pressure, then using an
ohmmeter check for continuity between pins 3,5 and 7. Approximately 10 ohms resistance is read between all
combinations of these three pins on a good tube. If open, replace the tube. Never check while under vacuum as the
ohmmeter may burn out the gauge tube. Pins 1 and 2 should show zero ohms. Trouble shooting the electronics is
difficult because this is a closed loop feed-back circuit. If circuit problems develop, it is best to return it to the
factory for repair.

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