HMR4007
SENSOR PRODUCTS
HMR4007
Linear Position Sensor
User's Guide
Solid State Electronics Center
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Page 1
HMR4007
SENSOR PRODUCTS
INTRODUCTION
The Honeywell HMR4007 is an electronic linear position sensing solution for use in commercial and industrial
application environments. A stationary array of Honeywell's magnetoresistive (MR) sensors is utilized to quickly and
accurately monitor the position of a small magnet attached to a moving object such as a valve stem or hydraulic
cylinder. The use of a sensor array makes the solution highly insensitive to many environmental influences such as
magnet strength, alignment, run out, and temperature. This solution is easily integrated into systems using a highly
reliable serial interface or a 12-bit analog output (with over-range error indication).
In normal operation, a small target magnet is mounted to the
moving object whose position is to be monitored and the sensor
array is held stationary. The exact standoff distance (gap) is
arbitrary (between 1/2" to 1-1/2") as the embedded software is
highly tolerant of this gap. The sensed axis is parallel to the long
axis of the sensor board. The embedded software then
calculates the position of the magnetic center of the target
magnet as a function of its distance along the axis of the board.
The result is expressed as a 12-bit unsigned integer (or as a 12-
bit analog voltage). In the example to the left, if the center of the
magnet was aligned with the center of the bottom-most sensor in
the array, the result would be interpreted as a position of "0" while
alignment with the top-most sensor would be interpreted as a
position of "4095". To convert the reading to engineering units,
the reported position is divided by 4095 and then multiplied by the
span of the sensors (69.7mm or 2.75"). If we call the reported
position "x", then the position in engineering units would be:
N
~0.5 - 1.5"
moving object
stationary sensor card
Position in mm = (x / 4095) * 69.6
Position in inches = (x / 4095) * 2.75
The above example shows a magnet oriented in what is called the "radial" mode, where the magnetic poles point
towards the sensor card. The embedded software is also capable of operating with a magnet oriented in the axial
mode where the magnet poles point along the axis of the sensor as seen below. The sensor card, however, does
not automatically detect the magnet mode, and a status bit in the embedded code must be set to configure the
HMR4007. Software tools are available from Honeywell to easily accomplish this.
Radial mode magnet
"Axial" mode magnet
N
S
N
S
The orientation of the north and south poles is arbitrary, and the embedded software is highly tolerant of the magnet
geometry so that rectangular bar magnets or cylindrical magnets can be used equally well. Cylindrical magnets in
the axial mode are particularly attractive because the magnetic field is symmetrical with respect to rotation about the
center axis without loss of position accuracy.
The magnet should have a minimum length of 23mm (0.91 inches) along the axis of the travel. Shorter magnets,
however, can be used with some increase in the minimum gap between the magnet and sensor board as long as a
minimum field strength of 80 gauss and an apparent magnet length of 23 mm is maintained at the sensor board.
More on apparent magnet length can be found in the application notes at the end of this document.
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Page 2
HMR4007
SENSOR PRODUCTS
SPECIFICATIONS
Characteristics
Conditions
Min
Typ
Max
Units
General
Accuracy
0.2
0.1
mm
Resolution
0.1
mm
Hysteresis
0.01
mm
Repeatability
0.01
0.1
mm
Update Rate
10
30
Hz
Standoff
Distance (gap) between the target
magnet and the sensor board
0.1
5
(note 1)
mm
Magnetic Field
Range
magnetic field at the sensor array
80
(note 1)
gauss
length
apparent magnet length at sensor array
23
(note 3)
mm
Orientation
Axial
(note 2)
Electrical
Input Voltage
Unregulated
6
28
VDC
Current
15
20
mA
Digital Interface
Baud Rate
nonstandard synchronous serial interface
1000
21,000
Bits / sec.
Signaling Level
TTL levels
( "1" )
( "0" )
3.5
-0.3
5.0
1.5
VDC
VDC
Connector
In-Line 6-Pin Block (0.1" spacing)
Analog Interface
Analog Output
D/A output
0
2.5
VDC
Update Rate
10
30
Hz
Signaling Level
TTL levels
( "1" )
( "0" )
3.5
-0.3
5.0
1.5
VDC
VDC
Connector
In-Line 4-Pin Block (0.1" spacing)
Physical
Dimensions
Circuit Board Assembly
(including connectors)
40.0 x 80.0 x
12.0
mm
Weight
HMR4007
16.5
grams
Environment
Temperature
Operating
Storage
-40
-55
-
-
+70
+125
C
Note 1: The standoff distance between the sensor board and the target magnet is highly variable. A magnet of sufficient strength,
however, must be used to maintain a magnetic field strength of 80 gauss (min.) at the sensor array and an apparent
magnet length of 23 mm.
Note 2: Sensor boards are factory calibrated in the axial mode using a 27mm cylindrical magnet. Operation in the radial mode
must be configured by the user.
Note 3: cf. "Magnet Considerations" (pg. 8)
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HMR4007
SENSOR PRODUCTS
PIN CONFIGURATION
Pin Number
Pin Name
Description
Digital Interface
1
RTS
Serial Clock Output
2
Data_Out
Serial Data Output
3
Data_In
Serial Data Input
4
CTS
Serial Clock Input
5
Power
Unregulated Power Input (+6 to +28 VDC) (see note 1)
6
GND
Power and Signal Ground
Analog Interface
1
Power
Unregulated Power Input (+6 to +28 VDC) (see note 2)
2
Analog Out
0 - 2.5 VDC analog output
3
Position Valid
TTL level (0 = position invalid, 1 = position valid)
4
GND
Power and Signal Ground
Jumper Block #1
2-5
Note 1
Analog Output port selected as power source
3-6
Note 1
Serial Communications port selected as power source
Note 1: The board contains three interface connectors for digital and/or analog communications. Power is supplied to the board
through any one of these connectors and is selected by jumper block #1. All of the ground connections on all three
ports are common to the circuit ground and are not affected by the jumper position. Only ONE of the three positions on
JP1 should be shorted at a time. Shorting more than one may result in excessive power supply currents and board
damage.
CIRCUIT DESCRIPTION
The HMR4007 Linear Position Sensor circuit board includes all of the basic sensors and electronics to provide a
digital indication of position of a target magnet. The HMR4007 starts with an array of seven Honeywell HMC1501
single axis magnetoresistive (MR) sensors to determine the field geometry and direction of a target magnet attached
to the moving part of a device under test. These sensors are supplied power by a constant voltage source, and the
use of an array of sensors helps to maintain accuracy over temperature and run-out. The sensor outputs are routed
to a multiplexed Analog to Digital Converter (ADC) integrated circuit. A microcontroller integrated circuit periodically
queries the multiplexed ADC and performs sensor offset and gain corrections and computes the position of the target
magnet as a function of the distance of travel along the long axis of the sensor board. The position data, along with
an error bit, is available thought the serial interface or is present on the Digital to Analog Converter (DAC) output port.
The serial interface is not needed in order to use the board's stand-alone analog output. The microcontroller
also performs the external serial data interface and other housekeeping functions. An onboard EEPROM integrated
circuit is employed as a nonvolatile storage to retain necessary data and configuration variables for best performance.
The HMR4007 uses an on-board low drop out (LDO) +5 volt regulator so that a regulated +5 volt power supply or an
unregulated power supply in the range of +6VDC to +28VDC can be used. The power is supplied to the board
through one of the three user ports being (serial, analog, or USB) and a jumper is used to select which port is the
power source. Only one jumper should be in place at any one time as the board does not have over current
protection and use of more than one jumper can result in excessive power supply currents and board damage.
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HMR4007
SENSOR PRODUCTS
PHYSICAL CHARACTERISTICS
The circuit board for the HMR4007 Linear Position Sensor is approximately 340mm by 80mm. A 6-pin right angle
connector (J1) and two 4-pin connectors (J2, J3) protrude from the back of the board for user connections.
Components on the top-side have a maximum height of 12mm. Figure 1 shows a typical circuit board with
dimensions.
PARTS PLACEMENT
4 5
6
1 2
3
4 5
6
1 2
3
6 5 4 3 2 1
4 3 2 1
PC (parallel port)
Sens or Board
LPT bit
LPT pin
J1 pin
uP bit
function
color
S3
1 5
<
1
RA3
Tx_CLK
(gray)
S4
1 3
<
2
RA2
Tx
(yellow )
D1
3
>
3
RA1
Rx
(blue)
D0
2
>
4
RA0
Rx_CLK
(w hite)
-
-
< >
5
Vcc
+ 5 -2 8 VDC
(red)
-
1 9
< >
6
GND
pow er gnd
(black)
Sx = status (LPT port bas e address + 1 , Bit x)
Dx = data
(LPT port bas e address + 0 , Bit x)
Sensor Board
J2 pin
uP pin
function
1
Vcc
pow er input (5 -2 8 VDC)
2
RA4
status (TTL output)
Logic 0 = output not valid
Logic 1 = output valid
3
D/A Output
analog output (0 - 2 .2 5 V)
4
GND
pow er ground
Not used
leave all OPEN
4-40NF mounting holes
(connected to ground plane)
USB port
not used
Sensed axis
1 2 3
JP1
Where 1= J3 (USB)
2= J2 (Analog output)
3 =J1(digital communications) - shown above
Figure 1 Sensor board layout and connector pin designations
MATING PARTS
Connectors J1, J2, and J3 mate with GC/Waldom C-Grid crimp-style shells and terminals. Polarized shells (with a
locking tab) or unpolarized shells are available. The applicable GC/Waldom part numbers are:
Connector
pins
Polarized shell
Unpolarized shell
Crimp terminals
J1
6
50-57-9406
50-57-9006
16-02-0097
J2
4
50-57-9404
50-57-9004
16-02-0097
J3
4
50-57-9404
50-57-9004
16-02-0097
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