US Digital

EM1 Transmissive Optical Encoder Module

Overview

Two channel quadrature output with index pulse
TTL Compatible
Single +5V supply
Resolutions up to 2500 CPR (10,000 PPR)
Internal bypass capacitor
-55C to 125C operating temperature

The EM1 is a transmissive optical encoder module. This module is designed to detect rotary or linear position when used together with a codewheel or linear strip. The EM1 consists of a lensed LED source and a monolithic detector IC enclosed in a small polymer package. The...

Product Specifications

CPI/CPR	1" Disk With Index	2" Disk With Index	Linear Strip With Index
32	EM1-1-32	-	-
64	-	EM1-1-32*	-
120	-	-	EM1-0-120
125	-	-	EM1-0-127*
127	-	-	EM1-0-127
150	-	-	EM1-0-150
200	-	-	EM1-0-200
250	-	-	EM1-0-250
500	-	-	EM1-0-500
720	EM1-1-720	-	-
900	EM1-1-900	-	-
1000	EM1-1-1000	-	-
1024	EM1-1-1024	-	-
1250	EM1-1-1250	-	-
1800	-	EM1-2-1800	-
2500	-	EM1-2-2500	-

*Some modules can be used with other-than-native OD and/or CPI/CPR while maintaining specified tolerances.

Parameter	Min.	Max.	Units	Notes
Temperature	-55	125	C
Supply Voltage	4.5	5.5	Vdc	Ripple (<100mV P-P)
Load Capacitance	-	100	pF
Count Frequency	-	100	kHz	(rpm/60) x cycles/rev.
Disk Radial Position Tolerance	± .005		inch	with gap set by standard spacer tool

Specifications apply over entire operating temperature range.
Typical values are specified at Vcc = 5.0Vdc and 25°C.

Parameter	Min.	Typ.	Max.	Units	Conditions
Output Voltage	-0.5	-	Vcc	Vdc
Supply Current (32-250 CPR)	-	27	30	mA
Supply Current (500-2500 CPR)	-	55	57	mA
Low-level Output	-	-	0.5	Vdc	I_OL = 8mA max.
High-level Output	2.0	-	-	Vdc	I_OH = -8mA max.
High-level Output	4.2	4.8	-	Vdc	Unloaded
Output Current Per Channel	-8	-	8	mA

Encoding Characteristics:

Specifications apply over entire operating temperature range.
Values are for the worst error over full rotation.
Refer to timing diagram below.

Parameter	Symbol	Min.	Typ.	Max.	Units
Cycle Error		-	3.0	5.5	°e
Symmetry		150	180	210	°e
Quadrature		45	90	100	°e
Index Pulse Width	Po	60	90	120	°e
Ch. I Rise After Ch. B or Ch. A Fall	t1	10	100	250	ns
Ch. I Fall After Ch. B or Ch. A Rise	t2	70	150	300	ns

Timing Diagram:

CPR (N): The number of Cycles Per Revolution.

One Shaft Rotation: 360 mechanical degrees, N cycles.

One Electrical Degree (°e): 1/360th of one cycle.

One Cycle (C): 360 electrical degrees (°e). Each cycle can be decoded into 1 or 4 codes, referred to as X1 or X4 resolution multiplication.

Symmetry: A measure of the relationship between (X) and (Y) in electrical degrees, nominally 180°e.

Quadrature (Z): The phase lag or lead between channels A and B in electrical degrees, nominally 90°e.

Index (CH I.): The index output goes high once per revolution, coincident with the low states of channels A and B, nominally 1/4 of one cycle (90°e).

Position Error: The difference between the actual shaft position and the position indicated by the encoder cycle count.

Cycle Error: An indication of cycle uniformity. The difference between an observed shaft angle which gives rise to one electrical cycle, and the nominal angular increment of 1/N of a revolution.

Parameter	Torque
Mounting Screws	3.5 in.-lbs

Product Description

The EM1 is a transmissive optical encoder module. This module is designed to detect rotary or linear position when used together with a codewheel or linear strip. The EM1 consists of a lensed LED source and a monolithic detector IC enclosed in a small polymer package. The EM1 uses phased array detector technology to provide superior performance and greater tolerances over traditional aperture mask type encoders.

The EM1 module provides digital quadrature outputs. A third index channel output comes standard on all resolutions. Power is supplied from a single +5Vdc source. The single-ended outputs are capable of sinking or sourcing 8mA each.

The resolution of the modules and encoder disks or linear strips must match. Two mounting holes are provided to accept #4-40 machine screws. Because there is clearance in these mounting holes they should not be relied upon for accurate positioning; instead, mounting assemblies should incorporate two alignment pins (nominal diameter 0.095") just in-board of the mounting holes (see drawing).

For open collector and higher voltage applications, add the PC3 cable driver, or for differential cable driver outputs, add the PC4 cable driver. Encoder disks, linear strips, quadrature decoder chips, counter chips, computer interface boards, mating connectors and cables are also available.