Knowledgebase

Regular maintenance of the rotator primarily consists of keeping the external surfaces of the system clean by wiping them with a towel moistened with water or a mild, non-abrasive cleaner.

After about two weeks of continuous use, open the brush chamber and vacuum out any dust or debris. If necessary, remove the lower bearing assembly for better access to the brush chamber (see Section 6.3), and use a towel moistened with water or a mild, non-abrasive cleaner to clean the inner surfaces of the brush chamber.

The electrode brushes may deposit silver-carbon dust inside the brush chamber and deposit a film on the surface of the rotating shaft. A thin film on the shaft actually improves the contact between the brush and the shaft. This film does not need to be cleaned off of the shaft unless the film is rough or bumpy.

The brushes contact the rotating shaft, slowly wearing during normal use, and periodically, the brushes must be replaced. A simple brush replacement kit is available, or in the case of serious damage to the entire brush assembly, the brush and its PTFE holder can be replaced.

1. The standard brush replacement kit contains a small hex key, a new brush, and a new set screw (installed in the brush).
   A special brush replacement kit should be used when the rotator is routinely operated in low humidity conditions such as inside a glove box.
   Part numbers for brush replacement kits are listed in Section 7.1.

2. Remove the entire brush assembly from the rotator by unscrewing it as shown below. It should be possible to remove the brush assembly by hand.


NOTE:

The brush is spring-loaded. When you remove the set screw in the next step (below), the brush will tend to fly out of the brush holder. Use a finger to hold it in place as you are removing the set screw.

3. Use the small hex key to remove the set screw. Note that the required hex key () is included with the brush replacement kit.

4. After removing the set screw, remove and discard the old brush, but do not discard the empty brush holder.

5. The new replacement brush includes a set screw which is already installed.
   • Temporarily remove this set screw.
   • Be careful not to misplace the set screw.

6. Carefully slide the new spring-loaded brush into the brush holder.
   Be careful to properly align the set screw hole with the slot on the side of the brush holder.

7. While squeezing the new brush into the brush holder, use the hex key to reinstall the set screw.
   Tighten the set screw until it stops turning.


NOTE:

The set screw should protrude slightly into the slot, and the brush should be free to travel to the extent permitted by the width of the slot.

8. Reinstall the brush assembly by threading it back into the side of the rotator.
   Hand-tighten the brush assembly. Do not use tools to tighten the assembly.

In the event that the main body of the brush assembly is damaged, it may be necessary to replace the entire brush assembly.

1. Remove the old brush assembly from the rotator by unscrewing it as shown below.
2. Remove the old brush assembly by hand. (Use tools only if necessary!)

3. Install the new brush assembly by threading it by hand into the side of the rotator. Do not use tools to tighten the brush assembly.


INTENTIONAL WEAR PERIOD:

After installing a new brush, install a shaft and allow the rotator to run at for at least eight (8) hours. This rotation period wears a concave groove into the new brush. This intentional wear actually improves the electrical contact between the brush and the shaft.

The lower bearing assembly is a common replacement item due to mechanical wear and also due to exposure to corrosive vapors from the cell solution. The standard lower bearing assembly contains a stainless steel bearing which is generally resistant to corrosive attack. In laboratories where particularly corrosive solutions are used, an assembly based on a ceramic bearing can be used instead. Part numbers for bearing assemblies are listed in Section 7.1.

1. Disconnect the motor control cable from the connector on top of the motor unit. If there is a shaft presently installed the motor unit, remove the shaft. Disconnect any signal cables from the brush banana jacks (red and blue).
   Use a flathead screwdriver to loosen the four screws that secure the lower bearing assembly to the motor unit. As you are loosening the final screw with one hand, catch the bearing assembly with your other hand.


NOTE:

After the bearing assembly has been removed, it is a good idea to clean or vacuum out any debris in the brush chamber.

2. Align the four screw holes on the new bearing assembly with the four threaded holes in the motor unit.

3. Thread the four screws into the holes by hand. Then, tighten the screws with a flathead screwdriver.

On rare occasions (such as when replacing a failed motor), it may be necessary to remove the motor-coupling assembly from the motor unit.

1. Disconnect the motor control cable from the top of the motor unit.
2. If there is a shaft presently installed in the motor unit, remove the shaft.
3. Disconnect any signal cables from the brush banana jacks (red and blue).
4. There are two screws which hold the cowling in place (front and back). Use a flathead screwdriver to remove these two screws from the cowling.

5. Carefully begin removing the cowling from the motor unit. The internal cable assembly will prevent the cowling from being completely removed. However, there is a junction in the middle of the internal cable assembly where two white connectors are joined together. By disconnecting the cable assembly at this junction, it is possible to remove the cowling completely. Disconnect the junction by releasing the locking mechanism that holds the connectors together.

6. The internal cables are secured to the motor using two plastic cable ties. In order to remove the motor, the lower cable tie must be cut and removed.




CAUTION:
DO NOT REMOVE the upper cable tie. The upper cable tie protects the fragile connections to the motor.

ATTENTION:
NE RETIREZ PAS l’attache de câble supérieure.
L’attache de câble supérieure protège les câbles fragiles de connexion au
moteur.

NOTE:

The red (positive) and black (negative) lines are connected to the tachometer, and the white (positive) and green (negative) lines are connected to the motor.

7. There are four screws which hold the motor in place.
• Using a flathead screwdriver, loosen and remove these four screws.
• As the fourth and final screw is being removed, be sure to support the motor and brush chamber from below to prevent damage from a sudden fall.
• Carefully lower the motor out of the support while guiding the fragile motor and tachometer cables through the support.

8. Carefully separate the motor from the brush chamber.

After removing the old motor-coupling assembly (see Section 6.4), a new motor-coupling assembly may be installed.

1. Disconnect the motor control cable from the top of the motor unit.
2. Disconnect any signal cables from the brush banana jacks (red and blue).
3. Examine the new motor coupling unit.
   • Examine the new motor coupling unit. There should be one cable tie securing the cables to the motor (black) as shown below. Do not remove this cable tie.
   • Remove any extra cable ties (i.e., around the green part of the motor) so that the cable can move freely.

4. Align the threaded holes in the new motor with those in the brush chamber and push the motor up into the support. Carefully feed the cables through the hole as shown in the figure below.

5. Perform the following:
   • Secure the motor and chamber to the support using four screws.
   • Connect the internal cable within the cowling to the motor by joining the two white connectors together.
   • Replace the cowling on top of the motor and secure it with two screws.

Motor Control Cable Wiring

The motor control cable is a 15-conductor cable that is wired “straight thru” from a male HD-15 connector on one end to a female HD-15 connector on the other end. Although there are 15 conductors, only four signals actually travel through the cable, and several conductors are grouped together (see Table 6.1). The HD-15 connector on top of the motor unit connects (internally) with the motor wiring harness which has four colored signal wires (see Table 6.2).

pins	description
1-4	Motor Supply (-)
6-9	Motor Supply (+)
11-12	Tachometer (+)
13-14	Tachometer (-)

Table 6.1: Motor Control Cable Wiring

wire color	description
green	Motor Supply (-)
white	Motor Supply (+)
red	Tachometer (+)
black	Tachometer (-)

Table 6.2: Internal Motor Cable Wiring

The rotation rate is controlled by a tunable analog feedback circuit located inside the control unit. This circuit is tuned and calibrated at the factory prior to shipment, but if the rotator needs to be recalibrated by the owner at a later date, the procedure below describes the best method for calibrating and verifying the rotation rate control circuit.

The most important tool required for calibrating the rotator is a non-contact optical tachometer. Pine offers such a simple tachometer (see Figure 6.1) as part of the MSR Calibration Kit, and this simple tachometer is suitable for routine verification or calibration of the rotation rate by the owner. The MSR Calibration Kit is sold separately (see Section 7.1 for part number).

In the event that the rotation rate must be rigorously traceable to a national or international standards organization, a more sophisticated and professional tachometer with traceable certification should be used (see Figure 6.2). When a rotator is manufactured at the factory (or when a rotator is returned to the factory for service), recalibration is performed using a traceable tachometer.

The tachometer reads the rotation rate when it is pointed at a rotating shaft equipped with a reflective target (see Figure 6.3). The MSR Calibration Kit includes a shaft suitable for use as a target. Alternately, a stainless steel rod (; ) may be mounted in the motor coupling, and a mark can be made on the rod with a marker.

   

Figure 6.1: Rotator Calibration Toolkit (including simple handheld tachometer)

Figure 6.2: Professional Optical Tachometer with Traceable Calibration

 

Figure 6.3: Use of Optical Tachometer with Reflective Target

The calibration process involves making adjustments to various trimmer potentiometers (trimmers) on the circuit board. The MSR Calibration Kit includes a trimmer adjustment tool for this purpose. Alternately, a small flathead screwdriver can be used to make these adjustments.

A calibrated digital voltmeter is required to confirm certain signal levels on the circuit board. It is recommended that a digit voltmeter be used for this purpose. The calibration process also requires a known voltage source (). This known source can be a power supply or waveform generator, and the value of the known voltage () should be verified using the calibrated digital voltmeter.

Other tools required are a medium sized Phillips screwdriver (to remove the top panel of the control unit) and a small () hex key (to turn the hex screws on the motor coupling when installing or removing a shaft). The hex key is included with the purchase of a new rotator and it is also available at many retail hardware supply stores.

DANGER:

High voltage. Risk of electric shock.

This procedure must be performed by an electrician or a qualified technician. This procedure requires working inside the control unit while the control unit is powered on and operating.

High voltages are present inside the control unit at the power entry module and on the two internal power supply modules as shown in the shaded and outlined portion of the image below.

KEEP HANDS AND TOOLS AWAY FROM THE POWER ENTRY MODULE AND THE TWO POWER SUPPLY MODULES!

DANGER:

Haute Tension. Risque de décharge électrique.

Cette procédure doit être confiées à un électricien ou un technicien qualifié. Cette procédure requiert de travailler à l’intérieur de l’unité de commande lorsque cette dernière est alimentée et en fonctionnement.

Des tensions élevées sont présentes dans l’unité de commande au niveau du module d’entrée d’alimentation et sur les deux modules d’alimentation internes tel qu’indiqué dans la portion grisée et mise en évidence de l’image ci-dessous.

GARDEZ VOS MAINS ET VOS OUTILS ÉLOIGNÉS DU MODULE D’ENTRÉE D’ALIMENTATION ET DES DEUX MODULES D’ALIMENTATION!

1. Switch off power to the rotator and disconnect the power cord.
2. With the power cord disconnected, remove the cover from the control unit.

3. While the power is switched off, note the positions of the various trimmers located along the top of the main circuit board.
   • A trimmer adjustment tool (or a flathead screwdriver) is required to adjust these trimmers.

4. While the power is switched off, install the tachometer target into the motor coupling on the motor unit.
   • This target should be a metal rod with the appropriate diameter ( or ).
   • Many tachometers require that a piece of reflective tape be attached to the end of the shaft as shown.

5. Turn the rotation rate knob fully counter-clockwise. This is the position which corresponds to a nearly zero rotation rate.
6. Reconnect the power cord and carefully switch on the rotator.

WARNING:

Laser radiation.

Many optical tachometers use a laser beam as a light source.

Do not look directly at the laser beam. Do not point the laser beam into the eye.

AVERTISSEMENT:

Rayonnement laser.

Un grand nombre de tachymètres optiques utilisent un faisceau laser comme source de lumière. Ne regardez pas directement le faisceau laser. Ne pointez pas le faisceau laser dans l’oeil.

7. Using the tachometer to monitor the actual rotation rate, slowly adjust the rotation rate knob on the front panel until the tachometer indicates a rotation rate of approximately .

WAITING PERIOD:

Allow the rotator to rotate at for one (1) hour before continuing with the calibration process. This waiting period permits all electronic and mechanical components of the rotator system to equilibrate and reach a steady state.

8. After the one hour waiting period, turn the rotation rate knob fully counter-clockwise. This is the position which corresponds to a nearly zero rotation rate.
9. Locate testpoints TP2 and TP3 on the circuit board.
   • These testpoints are accessible without the need to remove the circuit board from the control unit.

10. Connect the black lead of the digital voltmeter to one of the two black banana jacks (DC common) on the front panel of the control unit.

NOTE:

In the next several steps of the procedure, the red lead on the voltmeter is connected to various testpoints, but the black lead should remain connected to the DC Common jack on the front panel.

11. Connect the red lead of the digital voltmeter to testpoint TP3 on the circuit board.
    • Adjust trimmer P3 until the voltmeter reads .
12. Connect the red lead of the digital voltmeter to testpoint TP2 on the circuit board and keep it connected to perform the following steps.
    • Adjust trimmer P2 until the voltmeter reads .
    • Adjust trimmer P3 until the voltmeter reads approximately .
    • At this point, the motor should be rotating at a very slow rate. The direction of this slow rotation should be counterclockwise when looking down on the motor unit from above.
13. Turn the rotation rate control knob very slowly until the motor comes to a complete stop.
    • Adjust trimmer P7 until the rotation rate display on the front panel reads .
    • Connect the red lead of the digital voltmeter to the OUTPUT signal jack on the front panel. Confirm that the signal level at this jack is .
    • Using the tachometer to monitor the actual rotation rate, slowly adjust the rotation rate knob on the front panel until the tachometer indicates a rotation rate of .
14. While the shaft is rotating at , adjust trimmer P6 until the rotation rate display on the front panel of the control unit reads .
15. Connect the red lead of the digital voltmeter to the OUTPUT signal jack on the front panel. Confirm that the signal level at this jack is .
16. Slowly turn the rotation rate control knob counterclockwise until the motor comes to a complete stop.
17. Connect a DC voltage source to the rotation rate input signal jacks on the front panel of the control unit. The positive lead from the voltage source should be connected to the INPUT signal jack (gray banana jack), and the negative lead from the voltage source should be connected to the DC Common (black banana jack).
18. Determine the setting for the input rotation rate ratio () by carefully examining the position of jumper JP2 on the circuit board.


NOTE:

Some older control units may not have jumper JP2 on the circuit board. In this case, the input rotation rate ratio is printed on the front panel near the INPUT banana jacks.

19. Using the DC voltage source, apply to the rotation rate INPUT signal and observe the reading on the front panel display. The proper reading will depend upon the position of jumper JP2 as follows:
    • If JP2 is set for , the display should read .
    • If JP2 is set for , the display should read .
    • If JP2 is set for , the display should read .
20. Adjust P5 until the rotation rate display on the front panel is within the tolerance. The optical tachometer should also indicate a rotation rate within this tolerance.
21. Disconnect the voltage source from the INPUT jacks on the front panel.
22. Verify the calibration at the several different rotation rates (suggested rates are ).
    • At each rotation rate, the rotation rate display on the front panel, the rotation rate indicated by the optical tachometer, and the rotation rate indicated at the OUTPUT jack on the front panel should all agree to within one percent ().
    • The readings noted during this step should be recorded in a log book or on a certification sheet.

NOTE:

A convenient certification sheet that can be used to record the verification readings (from the previous step) can be found at the end of this procedure.

23. Switch off power to the rotator and disconnect the power cord.
24. Use a small () hex key to loosen the hex screws in the motor coupling and remove the shaft from the rotator.
25. Use the hex key to securely retighten the hex screws into the motor coupling.
26. Close the clamshell doors on the brush chamber and secure the latch.
27. Secure the enclosure around the rotator motor unit (see Figure 4.6).

WARNING:

Rotating shaft. Very high rotation rates!
The next part of the calibration procedure involves rotation rates at or above .
Before continuing, verify each of the following points:

• Verify that the shaft has been removed from the rotator.
• Verify that the hex screws in the motor coupling are tightened.
• Verify that the clamshell doors are closed and latched.
• Verify that the enclosure window is secured to all four pins as shown below.

AVERTISSEMENT:

Arbre en rotation. Vitesses de rotation extrêmement élevées!
La prochaine partie de la procédure d’étalonnage implique des vitesses de rotation supérieures ou égales à .
Avant de continuer, vérifiez chacun des points suivants:

• Vérifiez que l’arbre a été retiré du rotateur.
• Vérifiez que les vis hexagonales du raccord avec le moteur sont bien serrées.
• Vérifiez que les portes de la coque sont fermées et verrouillées.
• Vérifiez que les quatre broches de fermeture de la fenêtre du boîtier sont fermées tel qu’indiqué ci-dessous.


28. Turn the rotation rate knob fully counter-clockwise. This is the position which corresponds to a nearly zero rotation rate.
29. Reconnect the power cord and carefully switch on the rotator.
30. Slowly turn the rotation rate control knob fully clockwise to the fastest rotation rate.
    • The rotation rate display on the front panel of the control unit should read approximately .
    • Adjust trimmer P4 until the rotation rate display on the front panel of the control unit reads
    • Turn the rotation rate knob fully counter-clockwise. This is the position which corresponds to a nearly zero rotation rate.
31. Switch off power to the rotator and disconnect the power cord. While the power cord is disconnected, replace the cover on the control unit.

32. At this point the calibration procedure is complete. Make a note in a log book or place a sticker on the control unit to record the calibration date.

A blank calibration certificate can be found at the link below. Each time the rotator is (re)calibrated, it is a good idea to record the results of the calibration procedure on this form and then keep a copy of this form in a log book near the instrument.

The rotation rate can be controlled by applying an external voltage signal to the input jacks on the front panel of the control unit. The proportionality ratio used to convert the applied voltage signal to the rotation rate can be set to one of three different values: .

Normally, the value for the rotation rate ratio is selected to match the control signal provided by a particular potentiostat. When shipped from the factory, the MSR rotator is pre-configured with a ratio of because this ratio is compatible with Pine potentiostat systems.

1. With the power cord disconnected, remove the cover from the control unit.

2. Loosen the screw that secures the main analog board to the front panel, and then carefully remove the analog board.

3. On the board, locate the configuration pins with the designation JP2. There is a small jumper that can be used to short together one of three pairs of pins.

4. Place the jumper across one of the three pairs of pins at JP2.
   • Choose the ratio required for the particular potentiostat being used with the rotator.


       

(Note: MSR rotator factory setting is )

5. Reinstall the board in the control unit and secure the board to the front panel.

6. Replace the cover on the control unit.

7. At this point the input ratio has been changed. Make a note in a log book or place a sticker on the control unit to indicate the new input ratio.

The motor stop signal on the back panel of the control unit is a digital signal that can be used to bring the motor to a complete stop. This digital signal can be configured for either “active high” or “active low” logic.

The motor stop signal usually originates from a potentiostat that is controlling the rotator. A cable from the potentiostat applies the signal to the Motor Stop banana jack (blue) on the back panel. This signal is a TTL-type digital logic signal with a voltage level that is measured versus the DC Common (i.e., any of the black banana jacks on either the front or back panel).

If the motor stop signal logic is configured for “active HIGH” logic, the behavior is as follows: The motor is allowed to rotate if a signal greater than is applied to the blue Motor Stop banana jack. The motor is stopped if the Motor Stop signal is driven to DC Common (i.e., it stops if the blue Motor Stop banana jack is shorted to any of the black DC Common jacks).

If the motor stop signal logic is configured for “active LOW” logic, the behavior is as follows: The motor is stopped if a signal greater than is applied to the blue Motor Stop banana jack. The motor is allowed to rotate if the Motor Stop signal is driven to DC Common (i.e., it rotates if the blue Motor Stop banana jack is shorted to any of the black DC Common jacks).

Normally, the choice for the Motor Stop signal logic is selected to match the control signal provided by a particular potentiostat. When shipped from the factory, the MSR rotator is pre-configured with “active HIGH” logic because this logic is compatible with Pine potentiostat systems.

1. With the power cord disconnected, remove the cover from the control unit.

2. Loosen the screw that secures the main analog board to the front panel, and then carefully remove the analog board.

3. On the board, locate the configuration pins with the designation JP1. There is a small jumper that can be placed in one of two positions at this location.

4. Place the jumper across one of the two positions shown below.
   • Choose the position required for the particular potentiostat being used with the rotator.



Active LOW Position (AL) – Active HIGH Position (AH)

 

5. Reinstall the board in the control unit and secure the board to the front panel.

6. Replace the cover on the control unit.

7. At this point the motor stop signal logic has been changed. Make a note in a log book or place a sticker on the control unit to indicate the new logic.