Milltronics MD-256 Instruction Manual

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MD-256 Speed Sensor

33455430 Rev 1.0

Instruction Manual PL-543 April 1998

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hank you for purchasing Milltronics products. We endeavour to design

equipment that is simple to use and reliable in its operation, with the aim

of satisfying our customers' needs.

Milltronics has been designing and manufacturing process equipment since

1954. Our fields of expertise include ultrasonic and capacitance level

measurement, in-line weighing of dry bulk solids and motion sensing.

Milltronics is established world wide through associate offices and

representatives. Our network is continually being refined to provide our

customers with first rate sales information, engineering assistance and after

sales support.

For more details on our products and service, please contact us and we will

provide you with a listing of the offices or representatives nearest you.

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TABLE OF CONTENTS

Specifications 4

General Operation 5

Circuit 5

Installation 6

Dimensions 6 Mounting 7

Mounting to a Tail Pulley 8 Mounting to a Bend or Snub Pulley 9 General Installation Steps 10 Interconnection (Wiring) 11

Terminals 11

Terminal Connections to Integrators 12

Maintenance 13

Inspection 13

Bearing Replacement 13

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SPECIFICATIONS

Power

Ambient Temperature

Input

Output

Enclosure

Approval

Cable (optional)

Weight

+10 to +15V dc, 30mA (from integrator)

-40° to 55° C (-40°F to 131°F)

Shaft rotation 0.5 to 470 rpm, bidirectional

Unidirectional open collector sinking output

+5V dc, 25mA max (to integrator)

256 pulses per revolution

2 to 2000Hz

General purpose

Aluminum

3-wire shielded, 7.5mm2 (18 AWG)

Max run 305m (1000’)

1.22 kg (2.68 lb.)

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GENERAL OPERATION

The MD-256 is a digitizing speed sensor for use on belt scales. It connects to the shaft of a pulley and measures the shaft's rotation by sending pulses to the Milltronics integrator.

This speed sensor features:

High resolution for accurate measurement

Small size

Light weight

Long bearing life

CIRCUIT

256 pulses are generated for each rotation of the MD-256 shaft. These pulses are typically fed into a Milltronics belt scale integrator. The integrator interprets the pulses and uses them in the calculation of belt speed, flow rate, and material totalization.

Integrators with which the MD-256 works are:

Compuscale

Compuscale II

Compuscale IIA

CompuScale-III

Compu-M

Accumass BW-100

Competitive integrators – consult your local Milltronics representative

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INSTALLATION

Installation must only be performed by qualified personnel.

DIMENSIONS

50mm (1.96”)

305mm

(12.0”)

131mm

(5.16”)

Rod ∅: 8.0mm

(5/16” )

Shaft ∅: 15.9mm

(5/8")

102mm

(4.03”)

1/2" NPT conduit entrance

(optional PG13.5 adapter available)

102mm

4.00”

111mm

4.36”

159mm

6.25”

89mm (3.5”)

60mm (2.38”)

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1/2" NPT conduit entrance (optional PG13.5 adapter available)

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MOUNTING

The input shaft on the MD-256 is coupled to the rotating shaft on a belt driven pulley and is not externally supported. The unit’s arresting rod stops it from rotating with the shaft and can be fitted with a spring to soften sudden speed changes.

The arresting rod should only be solidly attached to the MD-256.

Fixing the rod at both ends will apply binding forces and cause

When mounting the unit ensure that it is concentric with the pulley shaft to avoid stresses on the unit’s bearings.

For preferred mounting locations, refer to the associated belt scale or weigh feeder instruction manual.

Manuals for these integrators are:

Compuscale PL-216 Compuscale II PL-261 Compuscale IIA PL-281 CompuScale-III PL-367 Compu-M PL-516 Accumass BW-100 PL-531

the unit’s bearings to wear prematurely.

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MOUNTING TO A TAIL PULLEY

Angle bracket slotted

for arrestor rod

≥10mm (.375”)

Angle bracket slotted

MD-256

for arrestor rod

Tension spring (supplied)

Belt

Flexible conduit

Tension spring

Arrestor rod (cut to suit)

89mm

3.5”

MD-256

Notes:

Flexible conduit

Distance “d” is the take up travel on the tail pulley

When adjusting the belt take up ensure that there is play on the arrestor rod. If the arrestor rod is pushed against the end of its travel slot then premature bearing wear may result.

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MOUNTING TO A BEND OR SNUB PULLEY

Tension spring (supplied)

Stringer

Bend or Snub pulley

Notes:

MD-256

Flexible conduit

Stringer

3/8” drilled hole for

arrestor rod

Tension spring

Pulley bearing

Belt

Arrestor rod (cut to suit)

90mm

3.5”

MD-256

Flexible conduit

When mounting to a bend or snub pulley only a 3/8” (10mm) drilled hole is required for the arrestor rod.

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GENERAL INSTALLATION STEPS

1. Drill out pulley shaft to a depth of 64mm (2.5”) concentric to its centerline.

Exercise

caution and remain within specified tolerances.

2. Drill out and thread the set screw hole

M8x1.25 (5/16-18 UNC) set screw (by customer)

64mm

(2.5”)

25mm

(1”)

16.00mm (.630”) DIA.

16.07mm (.633”)

3. Attach angle iron bracket to work with the arrestor rod (if mounting on a tail pulley)

4. Cut the arrestor rod to a suitable length

5. Insert the MD-256 shaft into the pulley shaft and lock with set screw on flat of shaft

6. Attach spring to arresting rod and frame

127mm

Example slot for arrestor rod when mounted to tail pulley – use drilled hole for snub or bend pulley

(5”)

approx.

Tension spring

Secure with bolt or post

Angle iron bracket or conveyor stringer

7. Encase wiring in flexible conduit to allow unit to float

8. Wire the MD-256 to the Milltronics’ integrator

Terminal Connections to Milltronics

See

Integrators on page 12 for terminal post

connections

The arresting rod should only be solidly attached to the MD-256. Fixing the rod at

both ends will apply binding forces and wear the unit’s bearings prematurely.

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INTERCONNECTION (WIRING)

All wiring must be done in conjunction with approved conduit, boxes and fittings and

Interconnection between the unit and the integrator should be made with 3-wire shielded, 18 AWG cable. Ground the shield at the integrator end ONLY.

TERMINALS

to procedures in accordance with all governing regulations.

Flexible conduit is recommended so that excess stress

is not applied to the shaft bearings.

1 – +15V dc

The positive power supply from the integrator connection

2 – Clockwise Speed out

The positive output connection of the measurement loop. This output is only used when the sensor is rotating clockwise.

3 – Counter-Clockwise Speed out

The positive output connection of the measurement loop. This output is only used when the sensor is rotating counter-clockwise.

4 – Common

The common connection used as a reference point with the integrator

GND – Ground

A ground connection. Do not use this ground for the cable shield.

Ground the cable shield at the integrator end only!

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TERMINAL CONNECTIONS TO MILLTRONICS INTEGRATORS

MD-256

Compuscale 1 2 2 4 N/C Compu II 15 16 16 14 N/C Compu IIA 12 13 13 14 N/C Compu-M 11 12 12 13 N/C Compu III 30 31 31 32 N/C Accumass BW-100 8 7 7 6 N/C

Determine the pulley shaft rotation on the end of the pulley shaft to which the MD-256 is attached.

If the pulley shaft is

If the pulley shaft is terminal 3.

N/C indicates that the terminal is not normally connected.

rotating clockwise

rotating counter clockwise

Do not connect terminals two and three at the same time.

+15V

then connect the appropriate wire to terminal 2.

CCW4Cmn

then connect the appropriate wire to

GND

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MAINTENANCE

INSPECTION

Periodically the cover should be removed and the enclosure and circuit board should be cleaned if dust or grime builds up. If cleaning is required, disconnect the power and use a vacuum cleaner and a clean, dry paint brush. While the cover is off check all electrical contacts for corrosion and evidence of arcing.

Bearing wear is detected by excess play or sound. If the bearings exhibit excess play or produce an unreasonably loud sound then they should be replaced.

BEARING REPLACEMENT

The unit’s bearings should be periodically checked for corrosion, wear, and seizing. The bearings' life depends on the mounting, the severity of the application and the surrounding environment. Sealed bearings are used so that lubrication is not required.

Printed circuit board

Shaft

Mounting screws

The bearing will wear prematurely if there is any force applied to the MD-256 body. Ensure that only flexible conduit is used on the unit and that it is not exerting force on the unit.

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Replacement Procedure

To replace the bearings when they are worn follow these steps.

Removing the Bearings

1. Remove the MD-256 cover

2. Remove the wiring from the terminal block

3. Remove the unit from its installation

4. Unscrew the circuit board fixing screws

5. Remove the circuit board and store in a static-free bag or equivalent “safe” area.

6. Remove the first bearing’s C clip (part A) using retaining ring pliers

7. Gently drift the unit’s shaft out of the housing. One bearing should come with the shaft and one should remain in the housing.

8. Pull the bearing off the shaft

9. Drift out the bearing and rawhide seal (part F) from the housing

10. Clean the housing with a rag

Replacing the Bearings

1. Warm the housing in hot water to expand the metal

2. Remove from the water and completely dry with a clean rag

3. Insert the rawhide seal (part F) into the housing

4. Slide one of the new bearings (part D) into the housing. Ensure it fits snugly against the end of the housing

5. Slide the second bearing onto the unit’s shaft

6. Gently drift the shaft back into place. It is in place when you can see the groove for the C clip (part A). Do not damage the pin on the end of the shaft as that is required to turn the encoder.

7. Replace the C clip (part A)

8. Replace the circuit board and ensure correct alignment of the rubber coupling and the shaft pins.

9. Replace the mounting screws for the circuit board

10. Reconnect to the installation

11. Rewire the terminal block

12. Replace the MD-256 cover

Replacement Parts

Part numbers and suppliers for the user-serviceable parts in the MD-256 are:

Part Supplier Part Number

Boston Bearings, 1623DCBearings (parts D)

Nice Bearings 16232RS

C Clip (part A) True Arc R3000-137 C Clip (parts C) True Arc R3100-62 Rubber Connector (part E) Milltronics 24300051 Dust Seal (part F) Chicago Seals 6141

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