Group3 DTM-151 User manual

Group3 Technology Ltd., 2 Charann Place, Avondale, Auckland 1026. P.O. Box 71-111, Rosebank, Auckland 1348, New Zealand.
Phone: [phone] Fax: [phone] email: [e-mail] web: www.group3technology.com
DTM-151
DIGITAL TESLAMETER
with IEEE-488 GPIB Interface
USER’S MANUAL
For units supplied with software DTMS V6.0 &V7.0
20 July 2007

Group3 Technology Ltd., 2 Charann Place, Avondale, Auckland 1026. P.O. Box 71-111, Rosebank, Auckland 1348, New Zealand.
Phone: [phone] Fax: [phone] email: [e-mail] web: www.group3technology.com
82010180
Thank you for purchasing and using a Group3 digital teslameter. We hope you will join
the many hundreds of users worldwide who are enthusiastic about our products.
Group3 has been designing and building magnetic field measuring equipment since
1983. We are constantly upgrading our products and support documentation. We
welcome input from our customers, so if there are aspects of the instrument which you
particularly like, or which you would like to see improved, please contact your Group3
supplier (see back page for a complete list) or Group3 directly with your suggestions to
[email protected].
The Group3 website, www.group3technology.com contains details of all our products.
This site is regularly updated, so check it from time to time to learn about recent
developments.
Group3 Technology Ltd.
2 Charann Place, Avondale, Auckland 1026
PO Box 71-111, Rosebank, Auckland 1348, New Zealand.
Phone: [phone]
Fax: [phone]
Email: [email protected]
Web: http://www.group3technology.com

DTM-151 (GPIB) User's Manual Contents-1
CONTENTS
1. General Description 1-1
2. Specifications of DTM-151 System 2-1
3. Setting Up
3.1 Introduction 3-1
3.2 Connecting the Hall Probe 3-1
3.3 Connecting the Power Source 3-2
3.4 GPIB Connection 3-4
3.5 Internal DIP Switch Settings 3-6
3.6 Analog Outputs 3-10
3.7 Grounding 3-11
3.8 Installing the Panel Mount Option 3-12
3.9 Installation Techniques for Electrically Noisy Environments 3-13
4. Operating Instructions
4.1 Zeroing 4-1
4.2 Installing the Probe 4-2
4.3 Reading the Field Value 4-3
4.4 Display Modes, Using the Front Panel Keys 4-4
4.5 Using the IEEE-488 GPIB Interface 4-7
4.6 Digital Filtering 4-20
4.7 Triggered Operation 4-21
5. Technical Diagrams
General Information 5-1
Display Board Schematic 5-2
Display Board Component Overlay 5-3
Display Board Parts List 5-3
Probe Plug Board Schematic 5-4
Probe Plug Board Component Overlay 5-5
Probe Plug Board Parts List 5-5
Processor Board Schematic 5-6
Processor Board Component Overlay 5-7
Processor Board Parts List 5-8
Analog Board Schematic 5-9,10
Analog Board Component Overlay 5-11
Analog Board Parts List 5-12,13

Contents-2 DTM-151 (GPIB) User's Manual
LIST OF FIGURES
Fig. 1 Power Input Connections of the -L option 3-3
Fig. 2 IEEE-488 Standard Connector 3-5
Fig. 3 Location of Processor Board Switches 3-7
Fig. 4 Panel Cutout Dimensions 3-12
Fig. 5 Probe Dimensions 4-3
Fig. 6 A Typical IEEE-488 System 4-7
Display Board Schematic 5-2
Display Board Component Overlay 5-3
Display Board Parts List 5-3
Probe Plug Board Schematic 5-4
Probe Plug Board Component Overlay 5-5
Probe Plug Board Parts List 5-5
Processor Board Schematic 5-6
Processor Board Component Overlay 5-7
Processor Board Parts List 5-8
Analog Board Schematic 5-9,10
Analog Board Component Overlay 5-11
Analog Board Parts List 5-12,13
LIST OF TABLES
Table 1 GPIB Connector Pin Assignments 3-4
Table 2 DIP Switch Functions 3-7
Table 3 String Terminator Switch Settings 3-8
Table 4 Analog Output Connector Pin Assignments 3-10
Table 5 IEEE-488 Command Codes 4-10
Table 6 DTM-151-_G IEEE-488 Command Codes 4-14
Table 7 DTM-151-_G IEEE-488 Commands 4-15,16,17

DTM-151 (GPIB) User’s Manual 1-1
1 GENERAL DESCRIPTION
The DTM-151-_G Digital Teslameters offer accurate, high resolution measurement of
magnetic flux densities, with direct digital readout in tesla or gauss, and IEEE-488 GPIB
interfacing for system applications. The instruments are light and compact, and the
probes are easy to use. The DTM-151 has been engineered to withstand the severe
electrical interference produced by high voltage discharge.
This description includes features of the serial communications option which is an
alternative to the IEEE-488 option. If your teslameter is the serial version, refer to the
DTM-151-_S User's Manual.
FEATURES
Measures magnetic fields over four ranges up to 3 tesla with polarity indication;
resolution up to 1 part in 600,000.
Used with special miniature Hall probe - easy to attach to magnet pole or other
hardware. Probe holders are available as optional accessories.
Accuracy and temperature specifications include total system performance, probe and
instrument. This is the only meaningful indication of measurement accuracy.
Probe is calibrated, with field and temperature characteristics stored in memory chip
contained in cable plug.
Basic accuracy 0.01% of reading + 0.006% of full scale.
Microprocessor reads probe calibration data stored in probe connector and computes
corrected field reading.
Temperature coefficient 10ppm/°C overall achieved using temperature sensor in probe.
Microprocessor calculates corrected field reading.
Accuracy is verified against nuclear magnetic resonance (NMR) standard.
Probe calibration is verified at many field points, and a printed calibration table is
supplied with every probe.
AC mode measures and displays time-varying fields between 8 Hz and 3000 Hz.
Front panel keys set the display to read the desired field range, to read the peak value
of the field using the peak hold function, to show the ac field component, and to display
the probe temperature.
Peak hold is implemented digitally, has zero sag.

1-2 DTM-151 (GPIB) User’s Manual
Digital filtering of the displayed field reading suppresses short-term fluctuations. The
filtering characteristic is non-linear; small field variations within a narrow window
centered on the currently displayed value are filtered; large field changes are displayed
immediately. Filter window and time-constant may be changed by remote command.
Filtering is controlled by an internal switch.
Two digital communication options: either serial (RS-232C and fiber optic)
or IEEE-488 General Purpose Interface Bus.
With the serial option, a single teslameter may be connected to standard RS-232C
equipment, or up to 31 units may be interconnected on a Group3 Communication Loop
(G3CL) and driven from computer or terminal.
Fiber optic ports duplicate functions of RS-232C signals, for electrical noise immunity
and voltage isolation. Fiber optic links may be up to 60 meters in length, using
Hewlett-Packard HFBR-3500 series fiber optic cables. Use a Group3 fiber optic repeater
to extend communication distance.
The IEEE-488 option fully supports all relevant GPIB functions and commands, including
full talker-listener capability, serial and parallel polling, service request, and talker-only.
ASCII control commands are accepted to modify the output data format, to change the
rate of data transmission or to request transmission of a single field reading. Other
commands set scaling and offset, select the field range, select ac and peak hold
functions, turn on and off digital filtering and modify the filter characteristics. System
status may be determined remotely.
The system can be operated in triggered mode where field measurements by one or
more teslameters are triggered in synchronism with each other by external command.
Internal switches select serial data format and baud rate, device address, string
terminators, filtering, field units in gauss or tesla, data format, service request action,
EOI action, and perform system reset.
Two analog outputs are available: instantaneous field value (0 to 3 kHz), rectified
time-varying (ac) component of field, (8 Hz to 3 kHz).
All model variations are available without display and keys for true 'black box' magnetic-
field-to-computer interfacing.
A panel mount model with display is available.

DTM-151 (GPIB) User’s Manual 2-1
2 SPECIFICATIONS OF DTM-151 SYSTEM
Specifications include LPT-141 or MPT-141 Hall Probe.
Measurements field value and time-varying (ac) component of field
Field ranges 0.3 0.6 1.2 3.0 tesla full-scale,
3 6 12 30 kilogauss full-scale,
with polarity indication
maximum calibration field ±2.2 tesla, ±22 kilogauss
Resolution DC mode with digital filtering ON:
1 in 600,000 of bipolar span as shown on front panel display.
range display resolution serial/GPIB resolution
gauss tesla gauss tesla
0.3 tesla 0.01 0.000001 0.001 0.0000001
0.6 tesla 0.02 0.000002 0.01 0.000001
1.2 tesla 0.04 0.000004 0.01 0.000001
3.0 tesla 0.1 0.00001 0.01 0.000001
Resolution DC mode with digital filtering OFF, and AC mode:
1 in 120,000 of bipolar full-scale span in display:
range display resolution serial/GPIB resolution
gauss tesla gauss tesla
0.3 tesla 0.05 0.000005 0.001 0.0000001
0.6 tesla 0.1 0.00001 0.01 0.000001
1.2 tesla 0.2 0.00002 0.01 0.000001
3.0 tesla 0.5 0.00005 0.01 0.000001
20-bit digitizing of field reading.
Accuracy DTM-151 with LPT-141 or MPT-141 probe:
±0.01% of reading ±0.006% of full-scale max. at 25°C
Temperature DTM-151 with LPT-141 or MPT-141 probe:
Stability calibration: ±10 ppm of reading/°C max.
zero drift: ±(1 microtesla + 0.0003% of full-scale)/°C max.
add -3ppm/°C for each meter of probe cable
Time stability ±0.1% max. over 1 year

2-2 DTM-151 (GPIB) User’s Manual
Measurement rate 10 measurements per second
Response time Full-scale change of displayed field reading settles to within
resolution in less than 0.3 second (filtering off - see below)
Peak hold mode Displays maximum field since mode entered or reset.
Peak hold is implemented digitally with zero sag or decay.
AC mode Displays time-varying (ac) component of field;
frequency response: 8 Hz to 3 kHz at -3dB points.
response time-constant: 0.2 seconds.
average responding,
reads rms value of sinusoidally-varying field.
reading is not linearity or temperature corrected.
Display 7-character 7-segment alphanumeric display.
Indicators 8 back-lit legends for:
0.3 0.6 1.2 3.0 tesla range selected,
peak hold mode on, digital filtering on, tesla/gauss field units.
Display modes magnetic field, peak hold field, ac field, peak ac field
Digital filtering field value filtering smoothes out small fluctuations in the reading;
large, rapid field changes are not filtered;
internally switch selected.
Keys 2 keys for range selection, access to display modes,
zeroing field display, peak hold reset.
Digital interfacing serial option: RS-232C and fiber optic.
parallel option: IEEE-488 General Purpose Interface Bus.
Digital data format ASCII input commands and output responses.
Commands requests for field values,
setting and inspection of display and control modes,
field measurement triggering, entry of numerical values,
setting units, output data format, and filter characteristics,
test commands.
Output responses field value in tesla or gauss followed by optional T or G
and string terminator(s), system status,
numerical data requested by commands, messages.

DTM-151 (GPIB) User’s Manual 2-3
Serial bit rate 16 rates, switch selected, 50, 110, 134.5, 150, 200, 300, 600,
900, 1050, 1200, 1800, 2000, 2400, 4800, 9600, 19200 baud.
System orientation Group3 Communication Loop (G3CL) using serial ports,
simple loop for 31 devices, no multiplexer required;
GPIB with IEEE-488 option.
Fiber optic cable Hewlett-Packard HFBR-3500, 60 meters max.
Fiber optic repeater available for extended communications.
On-board switches serial baud bit rate selection, load defaults, device address,
filtering, string terminators, data format,
service request enable, EOI enable.
Analog outputs dc output - instantaneous field analog:
full-scale output: ±3V nominal
source impedance: 1000Ω
accuracy: ±10%
bandwidth: 3kHz at -3dB, rolloff 3-pole 60dB/decade
ac output - rectified analog of time-varying (ac) field:
frequency response: 8Hz to 3kHz at -3dB points
time-constant: 0.2 seconds
average responding, delivers rms value of sinusoidal field
full-scale output: 3V nominal
source impedance: 1000Ω
accuracy: ±12%
IEEE-488 functions SH1 source handshake capability
AH1 acceptor handshake capability
T5 talker (basic talker, serial poll, talk-only mode,
unaddressed to talk if addressed to listen)
TE0 no address extension talker capability
L4 listener
(basic listener, unaddressed to listen if addressed to talk)
LE0 no address extension listener capability
SR1 service request capability
RL0 no remote local capability
PP1 parallel poll capability (configured by controller)
DC1 device clear capability
DT1 device trigger capability
C0 no controller capability
GPIB connector standard Amphenol 57-20240 with metric standoffs

2-4 DTM-151 (GPIB) User’s Manual
Memory back-up user-entered data storage for 30 days with power off.
Power source ac: min 8V at 0.7Arms, max 15V at 0.4Arms
dc: min 9V at 0.5A, max 19V at 0.25A
ac line input plugpack supplied.
Power fuse on processor board: 1 amp antisurge 5 x 20mm
To obtain maximum spark protection, use PS12D7 power supply
and ferrite kit 11000036. See section 3.9.
L option: 115/208/230 V ac power input.
Enclosure aluminium, 217 x 125 x 50 mm, textured finish,
light tan colour, tilt stand fitted to bench models.
Ambient field Maximum operating field for instrument:
10 millitesla with single-range probe,
0.5 millitesla with multi-range probe.
Temperature range 0 to 50°C operating,
absolute maximum temperature of probe 60°C.
Instrument weight 1.2 kg, shipping weight 2.5 kg.
Probes LPT series, transverse types,
sensitive area 4 x 1.6mm,
probe head size:
LPT-141 and LPT-231: 14 x 14 x 2.5 mm
MPT series, miniature transverse types,
sensitive area 1.0 x 0.5mm,
probe head size:
MPT-132 MPT-230 MPT-141 MPT-231: 14 x 5 x 2 mm
Standard cable length: 2 meters.
Special cable lengths to 30 meters.
Probe cable is shielded.