AMI 1720 Manual

Revision 1 - July 2022
American Magnetics, Inc.
P.O. Box 2509, 112 Flint Road, Oak Ridge, TN 37831-2509, Tel: [phone], Fax: [phone]
MODEL 1720
DUAL LIQUID LEVEL INSTRUMENT
INSTALLATION, OPERATION, AND
MAINTENANCE INSTRUCTIONS
EXCELLENCE IN MAGNETICS AND CRYOGENICS
1 Cover Page

Revision 1 - July 2022

REV 1 I
AMERICAN MAGNETICS, INC. TABLE OF CONTENTS
Foreword ................................................................................. vii
Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vii
Contents of this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vii
General Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
Cryogen Safety Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .x
Safety Legend . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .x
Equipment Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
Other Manual Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xii
Introduction ...............................................................................1
Model 1720 Instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Dual Cryogenic (Capacitance-Based) Liquid Level Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Digitally-Controlled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
System Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Intuitive Human-Interface Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Measurement Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Real Time Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Valve Control Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Alternate Control Modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Analog Outputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Signal Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Model 1720 Front Panel Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Model 1720 Rear Panel Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Model 1720 Specifications @ 25°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Controller Modes Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Auto-Changeover Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Pre-Cool Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

ii REV 1
AMERICAN MAGNETICS, INC. TABLE OF CONTENTS
Installation............................................................................... 15
Unpacking and Inspecting the Instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Mounting the Model 1720 Instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Capacitance-Based Liquid Level Sensor Installation . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Connecting the Capacitance Sensor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Configuring an Autofill System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Normal Dual-Autofill System Setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Auto-Changeover System Setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Pre-Cooled System Setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Power Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Connecting the Analog Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
0-10 VDC Recorder Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4-20 mA Current Loop Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Operation ................................................................................ 31
Energizing the Model 1720 Instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Screen Navigation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Home Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Home Screen Footer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Editing a Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Navigating the Instrument Menus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Menu Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Screen Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Capacitance Level Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Configure the Instrument to Display Channel Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Alarms and Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Alarm Status Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Level-Based Alarms Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Time-Based Fill Alarms Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Multiple alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Configuring the Alarm Setpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Acknowledging an Alarm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Muting an Alarm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Configuring Relay Setpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

REV 1 III
AMERICAN MAGNETICS, INC. TABLE OF CONTENTS
Configuring the Normal Autofill Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
Flowchart of Normal Autofill Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Setting the Normal Autofill Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Enable the Normal Autofill function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Clearing the Autofill Timeout Alarm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Configuring the Auto-Changeover Autofill Function . . . . . . . . . . . . . . . . . . . . . . . . . . .53
Display for Auto-Changeover Autofill Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Flowchart of Auto-Changeover Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Setting the Auto-Changeover Autofill Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Enable the Auto-Changeover Autofill function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Clearing the Auto-Changeover Overall Timeout Alarm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Configuring the Pre-Cooled Autofill Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
Display for Pre-Cooled Autofill Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Flowchart of Pre-Cooled Autofill Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Setting the Pre-Cooled Autofill Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Enable the Pre-Cooled Autofill function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Clearing the Pre-Cooled Fill Timeout Alarm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Selecting the Appropriate Units on the Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63
Damping Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
Analog Output Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
Configuring the Analog Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Ethernet Connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
IP Addressing Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Serial Connectivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
Configuring the
RS-232 Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Abnormal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68
Capacitance Sensor Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Resetting the Instrument to Factory Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Shutting the Instrument Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69

iv REV 1
AMERICAN MAGNETICS, INC. TABLE OF CONTENTS
Calibration ............................................................................... 71
Setting the System Date and Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Capacitance-based Level Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Understanding the Sensor Active Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Relationship between Calibration and Sensor Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Variations in the Dielectric with Changing Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Capacitance-based Sensor Calibration Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Pre-Calibration Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Open Dewar Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Closed Dewar Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Presetting the Maximum and Minimum Calibration Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Completing the Closed Dewar Calibration Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Approximate Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Remote Interface Reference..................................................... 93
SCPI Command Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
Compatibility Support for the AMI Model 1700 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Compatibility Support for the Legacy AMI Model 286. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Undocumented Commands/Queries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
RS-232 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Serial port connector and cabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Command/return termination characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Ethernet Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Ethernet Connector. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Termination Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Port Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Command Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
System Related Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Display Configuration Commands and Queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Relay Configuration Commands and Queries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Alarms Configuration Commands and Queries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
HI/LO Configuration Commands and Queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
Measurement Commands and Queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Fill Control and Queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
A/B Configuration Commands and Queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

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AMERICAN MAGNETICS, INC. TABLE OF CONTENTS
Assignment Commands and Queries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Channel Calibration Commands and Queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Remote Units Commands and Queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Legacy Command Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Commands for Controlling the Units of Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Commands for Configuring Permanent Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
Querying the Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
Returning a Level Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
Service and Repair..................................................................123
Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123
User Replaceable Parts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123
Battery Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124
Low Battery Indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
Fuse Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126
Tools Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
Firmware Upgrades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127
Upgrade via Ethernet-Based File Sharing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Upgrade via SCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
Appendix................................................................................131
Serial (RS-232) and Contact Sense Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131
Ethernet Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133
Aux I/O Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134
Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135
Instrument Displays “LOSS OF SENSOR” Condition for LN2 Level Measurement . . . . . . . . . . . . . 135
Instrument Displays “SENSOR SHORTED” Condition for LN2 Level Measurement . . . . . . . . . . . . 135
System Test Screens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
System Logs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

vi REV 1
AMERICAN MAGNETICS, INC. TABLE OF CONTENTS
Glossary ................................................................................. 143
Abbreviations and Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
Index...................................................................................... 145

AMERICAN MAGNETICS, INC. FOREWORD
REV 1 VII
FOREWORD
PURPOSE AND SCOPE
This manual contains the operation and maintenance instructions for the
American Magnetics, Inc. Model 1720 Dual Liquid Level Control
Instrument and outlines applications for various system configurations.
Since it is not possible to cover all equipment combinations for all
systems, only the most common configurations are discussed. The
customer is encouraged to contact an authorized AMI Technical Support
Representative for information regarding specific configurations not
explicitly covered in this manual.
CONTENTS OF THIS MANUAL
Introduction describes the functions, specifications, and characteristics
of the Model 1720 Instrument. It provides illustrations of the front and
rear panel layouts as well as documenting the performance
specifications. Additional information is provided in the form of system
block diagrams.
Installation describes how the Model 1720 Instrument is unpacked and
installed in conjunction with ancillary equipment in typical systems.
Block-level diagrams document the interconnects for various system
configurations.
Operation describes how the Model 1720 Instrument is used to monitor
and automatically control liquid nitrogen levels.
Calibration describes the various calibration techniques for liquid
nitrogen level sensors.

VIII REV 1
AMERICAN MAGNETICS, INC. FOREWORD : GENERAL PRECAUTIONS
Remote Interface Reference documents all remote commands and
queries available through the Model 1720 Instrument RS-232 and
Ethernet interfaces. A quick-reference summary of commands is
provided as well as a detailed description of each.
The Appendix and Glossary sections support the information in the
sections listed above. See the Appendix section when referenced from
other sections. See the Glossary for any words or acronyms presented
in the above sections, requiring a more complete understanding.
GENERAL PRECAUTIONS
Cryogen Safety
One of the most common cryogenic liquids used is nitrogen. Liquid
nitrogen is extremely cold at atmospheric pressure (321°F). The
following paragraphs outline safe handling precautions for cyrogenic
liquids.
Personnel handling cryogenic liquids should be thoroughly instructed
and trained as to the nature of the liquids. Training is essential to
minimize accidental spilling. Due to the low temperature of these
materials, a cryogen spilled on many objects or surfaces may damage
the surface or cause the object to shatter, often in an explosive manner.
Inert gases released into a confined or inadequately ventilated space
can displace sufficient oxygen to make the local atmosphere incapable
of sustaining life. Liquefied gases are potentially extreme suffocation
hazards since a small amount of liquid will vaporize and yield a very
large volume of oxygen-displacing gas. Always ensure the location
where the cryogen is used is well ventilated. Breathing air with
insufficient oxygen content may cause unconsciousness without
warning. If a space is suspect, purge the space completely with air and
test before entry. If this is not possible, wear a forced-air respirator and
enter only with a co-worker standing by wearing a forced-air respirator.
Cryogenic liquids, due to their extremely low temperatures, will also burn
the skin in a similar manner as would hot liquids. Never permit cryogenic
liquids to come into contact with the skin or allow liquid nitrogen to soak
clothing. Serious burns may result from careless handling. Never touch
uninsulated pipes or vessels containing cryogenic liquids. Flesh will stick
to extremely cold materials. Even nonmetallic materials are dangerous
to touch at low temperatures. The vapors expelled during the venting
process are sufficiently cold to burn flesh or freeze optic tissues.
Insulated gloves should be used to prevent frost-bite when operating
valves on cryogenic tanks. Be cautious with valves on cryogenic

AMERICAN MAGNETICS, INC. FOREWORD : GENERAL PRECAUTIONS
REV 1 IX
systems; the temperature extremes they are typically subjected to cause
seals to fail frequently.
In the event a person is burned by a cryogen or material cooled to
cryogenic temperatures, the following first aid treatment should be given
pending the arrival and treatment of a physician or other medical care
worker:
1. If any cryogenic liquid contacts the skin or eyes, immediately flush the
affected area gently with tepid water (102°F  105°F, 38.9°C  40.5°C) and
then apply cold compresses.
2. Do not apply heat. Loosen any clothing that may restrict circulation. Apply a
sterile protective dressing to the affected area.
3. If the skin is blistered or there is any chance that the eyes have been
affected, get the patient immediately to a physician for treatment.
Containers of cryogenic liquids are self pressurizing (as the liquid boils
off, vapor pressure increases). Hoses or lines used to transfer these
liquids should never be sealed at both ends (i.e. by closing valves at
both ends).
When pouring cryogenic liquids from one container to another, the
receiving container should be cooled gradually to prevent damage by
thermal shock. The liquid should be poured slowly to avoid spattering
due to rapid boil off. The receiving vessel should be vented during the
transfer.
Introduction of a substance at or near room temperature into a cryogenic
liquid should be done with great caution. There may be a violent gas
boil-off and a considerable amount of splashing as a result of this rapid
boiling. There is also a chance that the material may crack or
catastrophically fail due to forces caused by large differences in thermal
contraction of different regions of the material. Personnel engaged in this
type of activity should be instructed concerning this hazard and should
always wear a full face shield and protective clothing. If severe spraying
or splashing could occur, safety glasses or chemical goggles along with
body length protective aprons will provide additional protection.
The properties of many materials at extremely low temperatures may be
quite different from the properties that these same materials exhibit at
room temperatures. Exercise extreme care when handling materials
cooled to cryogenic temperatures until the properties of these materials
under these conditions are known.
Metals to be used for use in cryogenic equipment application must
posses sufficient physical properties at these low temperatures. Since
ordinary carbon steels, and to somewhat a lesser extent, alloy steels,
lose much of their ductility at low temperatures, they are considered
unsatisfactory and sometimes unsafe for these applications. The

XREV 1
AMERICAN MAGNETICS, INC. FOREWORD : CRYOGEN SAFETY SUMMARY
austinetic Ni-Cr alloys exhibit good ductility at these low temperatures
and the most widely used is 18-8 stainless steel. Copper, Monel®, brass
and aluminum are also considered satisfactory materials for cryogenic
service.
CRYOGEN SAFETY SUMMARY
Cryogenic systems are complex systems with the potential to seriously
injure personnel or equipment if not operated according to procedures.
The use of safety mechanisms (pressure relief valves, rupture disks,
etc.) in cryogenic systems is usually necessary.
Recommended Safety Equipment
The use of proper safety equipment is necessary. Such equipment may
include, but not limited to, the following items:
• First Aid kit
• Fire extinguisher rated for class C fires
• Cryogenic gloves
• Face shield
• Signs to indicate that there are potentially dangerous cryogens in use in the
area.
SAFETY LEGEND
Instruction manual symbol: the product is marked with this
symbol when it is necessary to refer to the instruction manual in
order to protect against damage to the product or personal
injury.
Hazardous voltage symbol.
Alternating Current (Refer to IEC 417, No. 5032).
Off (Supply) (Refer to IEC 417, No. 5008).
On (Supply) (Refer to IEC 417, No. 5007).
WARNING The Warning sign denotes a hazard. It calls attention to a
procedure or practice, which if not correctly adhered to,
could result in personal injury. Do not proceed beyond a
Warning sign until the indicated conditions are fully
understood and met.
O
I

AMERICAN MAGNETICS, INC. FOREWORD : EQUIPMENT WARNINGS
REV 1 XI
CAUTION The Caution sign denotes a hazard. It calls attention to an
operating procedure or practice, which if not adhered to,
could cause damage or destruction of a part or all of the
product. Do not proceed beyond a Caution sign until the
indicated conditions are fully understood and met.
EQUIPMENT WARNINGS
Before energizing the equipment, the earth ground of the power
receptacle must be verified to be at earth potential and able to carry the
rated current of the power circuit. Using extension cords should be
avoided. However, if an extension cord must be used, insure the ground
conductor is intact and the cord is capable of carrying the rated current
without excessive voltage drop.
In the event that the ground path becomes less than sufficient to carry
the rated current of the power circuit, the equipment should be
disconnected from power, labeled as unsafe, and removed from place of
operation.
Do not operate this equipment in the presence of flammable gases.
Doing so could result in a life-threatening explosion.
Do not modify this equipment in any way. If component replacement is
required, return the equipment to AMI facilities as described in the
troubleshooting section of this manual.
If used in a manner not specified in this manual, the protection provided
by the design, manufacture and documentation of the Model 1720
Instrument may be impaired.

XII REV 1
AMERICAN MAGNETICS, INC. FOREWORD : OTHER MANUAL CONVENTIONS
OTHER MANUAL CONVENTIONS
This manual may often refer to measuring liquid nitrogen (LN2) when
referring to capacitance-based level measurement since nitrogen is by
far the most common cryogenic liquid measured by a capacitance-based
sensor. The capacitance sensor technology can be used to measure
most any cryogenic liquid, with the exception of liquid helium (LHe)
which requires a superconductor-based sensor.

AMERICAN MAGNETICS, INC. INTRODUCTION
REV 1 1
INTRODUCTION
MODEL 1720 INSTRUMENT
The AMI Model 1720 Liquid Level Instrument is a sophisticated
measurement and control instrument which provides monitoring of two
capacitance-based level sensors as inputs and provides for automatic
level control (autofill) based on user set parameters.
DUAL CRYOGENIC
(CAPACITANCE-BASED)
LIQUID LEVEL SENSORS
The Model 1720 Instrument is designed for use with up to two
capacitance-based sensors for cryogenic liquids (except for helium).
The Model 1720 Instrument must use an oscillator device to measure
cryogenic liquid levels. This instrument has internal oscillators if the
distance between the sensor and the instrument is less than or equal to
15 feet (457 cm) so no external oscillator is necessary. If the distance
between the sensor and the instrument is greater than 15 feet, an
external oscillator/transmitter unit is necessary. The instrument will
automatically configure itself at boot time to use the internal oscillator
unless the external oscillator/transmitter is connected to the BNC
connector on the rear panel.
DIGITALLY-
CONTROLLED
The Model 1720 contains a microcomputer which controls analog data
conversion, display/keypad functions, communications I/O, dry contact
closures, generation of analog output signals and relay control of a
mains power outlet for solenoid valve autofill applications.
SYSTEM FLEXIBILITY The Model 1720 instrument incorporates data converters to translate
signals between the analog and digital domains. Precision
instrumentation techniques and potentiometer-free designs are

2 REV 1
AMERICAN MAGNETICS, INC. INTRODUCTION : MODEL 1720 INSTRUMENT
100-240 VAC
50-60 Hz
400 VA
VALVE CONTROL
ETHERNET
AMERICAN MAGNETICS, INC.
OAK RIDGE, TN, USA
RS-232
AUX I/O
CHAN NEL 1
VALVE CONTROL
CHAN NEL 2
NOTE: TWO LIQUID LEVEL SENSORS OF
ANY LENGTH MAY BE CONNECTED
SOLENOID-OPERATED
FLOW VALVES
(OPTIONAL)
3/8 NPT NYLON
FEED-THROUGH
(OTHER MOUNTING
OPTIONS AVAILABLE)
ACTIVE
SENSOR
LENGTH
(SPECIFY)
TOTAL
SENSOR
LENGTH
SENSOR
FRONT PANEL
A PROPERLY CONNECTED WARM SENSOR CAN
READ ~ +2% UNTIL COOL
MODEL 1720 DUAL
LEVEL CONTROLLER REAR PANEL
OSCILLATOR CABLES
RG-59/U COAXIAL CABLE,
≤15 FT. LENGTH
(ADJUSTABLE)
POWER
OI
AMI
Americann Magnetics,, Inc.
Modell 1720
Liquidd Level
Instrument
Model 1720 System Diagram using internal oscillator/transmitter

AMERICAN MAGNETICS, INC. INTRODUCTION : MODEL 1720 INSTRUMENT
REV 1 3
100-240 VAC
50-60 Hz
400 VA
VALVE CONT ROL
ETHERNET
AMERICAN MAGNETICS, INC.
OAK RIDGE, TN, USA
RS-232
AUX I/O
CHAN NEL 1
VALVE CONT ROL
CHAN NEL 2
NOTE: TWO LIQUID LEVEL SENSORS OF
ANY LENGTH MAY BE CONNECTED
SOLENOID-OPERATED
FLOW VALVES
(OPTIONAL)
3/8 NPT NYLON
FEED-THROUGH
(OTHER MOUNTING
OPTIONS AVAILABLE)
ACTIVE
SENSOR
LENGTH
(SPECIFY)
TOTAL
SENSOR
LENGTH
SENSOR
FRONT PANEL
A PROPERLY CONNECTED WARM SENSOR CAN
READ ~ +2% UNTIL COOL
MODEL 1720 DUAL
LEVEL CONTROLLER REAR PANEL
OSCILLATOR CABLES
RG-59/U COAXIAL CABLE,
6 FT. LENGTH
POWER
OI
AMI
American Magnetics, Inc.
Model 1720
Liquid Level
Instrument
EXTENSION CABLES
RG-59/U COAXIAL CABLE,
500 FT. LENGTH
(ADJUSTABLE)
OSCILLATOR/
TRANSMITTERS
Model 1720 System Diagram using external oscillator/transmitters

4 REV 1
AMERICAN MAGNETICS, INC. INTRODUCTION : MODEL 1720 INSTRUMENT
employed throughout the Model 1720 Instrument to ensure long term
stability and accurate signal translation for a wide range of conditions.
DISPLAY The Model 1720 Instrument has a 4.3” diagonal measure TFT (Thin Film
Transistor) color liquid crystal display of 480 x 272 pixels. The display
has a 4-wire resistive touch overlay for easy operator input.
INTUITIVE HUMAN-
INTERFACE DESIGN
The Model 1720 instrument is designed to simplify the touch-screen
based user interface. All functions were analyzed and subsequently
programmed so that the most commonly used functions are addressed
with the least number of keystrokes. The menus are presented in a
logical fashion so that the operation of the Model 1720 is intuitive to the
user. Context-sensitive Help screens are also provided.
MEASUREMENT
FLEXIBILITY
The Model 1720 can be configured to monitor and display up to two
capacitance-based liquid level sensors. Set points can be assigned to
control two dry-contact relay outputs. The make or break function of
each relay can be set independently. Two solid-state relays allow mains
power to be switched according to set points to operate a solenoid-
operated valve or other load.
REAL TIME CLOCK The Model 1720 Instrument incorporates a real time clock, which can be
manually set or synchronized via NTP, with support for worldwide
timezones including automatic DST adjustment.
VALVE CONTROL
OUTPUT
The Model 1720 Instrument has two switched, 2 ampere at mains
voltage, outputs for energizing up to two solenoid operated flow valve or
other loads. The outputs are controlled by zero-crossing solid state
relays.
In the Normal mode, each output can be configured for independent
autofill operation. The fill start is triggered by a level reading. The fill is
stopped by reaching a user-set level, or exceeding a maximum fill time.
ALTERNATE CONTROL
MODES
In addition to the standard two-channel independent autofill
configuration, term the normal mode, the Model 1720 supports Auto-
Changeover and Pre-Cool control modes.
In Auto-Changeover mode, Channel 1 is assigned both valve control
outputs which can switch between two source tanks for uninterrupted
filling operation. When a source tank is depleted, the Model 1720 will
automatically switch to the alternate tank and the depleted tank can be

AMERICAN MAGNETICS, INC. INTRODUCTION : MODEL 1720 INSTRUMENT
REV 1 5
removed for refill or replaced with a full tank without interrupting the fill
operations.
In Pre-Cool mode, Channel 1 is assigned both valve control outputs
where one valve operates as a line vent in order to “pre-cool” the fill line
and minimize the introduction of vapor into the level-controlled target
tank. Once the cooling time has expired, the vent valve is closed and the
second valve control output opens the line to fill.
ANALOG OUTPUTS The Model 1720 Instrument has four analog outputs, two 0-10 VDC
voltage outputs and two 4-20 mADC current loop outputs. The 4-20
mADC loop outputs have 1500 VPK circuit isolation. The outputs can be
used simultaneously. The sources for any of the analog outputs can be
either one of up to two configured sensors (Channel 1 or 2). Multiple
outputs can be driven from the same source, if desired.
SIGNAL RELAYS The Model 1720 Instrument has four signal relays that change state
based on a measured input. The set points of these relays are user-
selectable as is their function, alarm on level above or below a set point.
Relays can be assigned to either channel.
CONNECTIVITY The Model 1720 Instrument has a 10Base-T Ethernet connection as well
as an RS-232 port for connecting to other equipment. The instrument
communicates remotely via a SCPI-based command set. The command
set is backward compatible with the AMI Model 286 instrument.

6 REV 1
AMERICAN MAGNETICS, INC. INTRODUCTION : MODEL 1720 INSTRUMENT
The Model 1720 Instrument allows for remote operation with an external
browser via TCP/IP connection. All commands that are available by
touching the local screen are available via the web browser
NOTE Using a web browser to connect to the instrument allows use of a
computer keyboard to enter text and numeric values which may
be more convenient when making a large number of changes.
Model 1720 (Normal mode) Via Web Browser