American Magnetics 150A User Manual

INSTALLATION, OPERATION AND MAINTENANCE

INSTRUCTIONS FOR THE AMI

LIQUID HELIUM LEVEL METER

I. INTRODUCTION

The American Magnetics, Inc. (AMI) Model 150A is a compact, fully portable Liquid Helium
Level Meter providing simple and easy operation. The instrument is battery operated and when
used in conjunction with an AMI LHe Level Sensor, provides a truly portable means of
measuring liquid helium levels at any location. The sensor connects to the instrument via a
standard DB9 connector. The instrument displays 0-100% of sensor maximum active length
immersed in LHe. The instrument can be used with AMI sensors with active lengths of up to 60
inches. The instrument is powered by sealed lead-acid batteries. A standard AC-DC adapter
(either 120VAC or 230VAC) is supplied with the unit for charging the batteries. Since battery
energy consumption is strongly dependent on the LHe level being measured, AMI has developed
a special "battery saver" circuit which reduces the power drain from the batteries as more of the
sensor becomes superconducting. Power requirements decrease as LHe level increases. A front
panel POWER LED is provided to indicate sufficient battery power exists to make an accurate
level reading.

MODEL 150A

II. SPECIFICATIONS (at 25 °C unless stated otherwise)

Input Power (instrument) Sealed lead-acid battery (6VDC)

Input Power (AC adapter)

Operating temperature (instrument) 0 to 50 °C non-condensing

Operating temperature (AC adapter) 0 to 40 °C non-condensing

Sensor active length range 1 inch to 60 inches

Linearity

Absolute Calibration 0.5% of full scale

Probe Current 75 mA nominal

Battery Life Typically 1,000 readings with a 60" sensor.

0.5% of full scale

90VAC to 132VAC 50/60 Hz, or 180VAC to 264VAC
50/60 Hz (depending on specified AC adapter model)

2% of full scale (from 0 to 50 ºC)

1 March 6, 2001

III. INSTALLATION

A. Carefully remove the instrument from the shipping carton and remove all the packing

material. Inspect the equipment for any physical damage that may have occurred during
shipment.

NOTE:

If there is any shipping damage save all packing
material and contact the shipping representative to file a
damage claim. Do not return the instrument to AMI unless prior
authorization has been received. (See Section IX)

B. Install the liquid helium sensor as per the AMI document "Installation, Operation And

Maintenance Instructions for the AMI Liquid Helium Level Sensor."

C. To facilitate mobility, the Model 150A is equipped with a single standard DB9 connector

which connects the instrument to a sensor. Connect the LHe sensor wires to the DB9
connector terminals as follows:

Wire Color DB9 Pin Number Signal Name

Red 1 I+

Yellow 6 V-

Black 7 I-

Blue 8 V+

IV. OPERATION

A. Connect the instrument to the sensor via the sensor (DB9) connector. Refer to Figure 1.
B. Depress the READ push-button switch on the front panel to read the LHe level. The

button should be held for sufficient time to allow the meter reading to stabilize.

NOTE:

The front panel LED should light to indicate sufficient
sensor current exists to make an accurate reading. The
instrument is calibrated to read the helium level directly on the
panel meter. If the LED does not light during the level
measurement, recharge the batteries. When the READ button is
released, the unit is automatically deenergized.

2 March 6, 2001

Fig. 1. Model 150A

3 March 6, 2001