Mitsubishi Motors and Serial Encoders

The Mitsubishi serial encoders listed in the next section are supported by this selection. Mitsubishi incremental encoders with A, B, and Z lines should be tested as Generic Incremental encoders.

Types Supported

The following list shows the Mitsubishi encoders that are currently supported by the TI-5000JX:

OSA/OSE253, OSA/OSE105 and OSA/OSE104 –

The OSA253, OSA105, OSA104 and OSE104 encoders appear to use 20 bits to represent one revolution for 1,048,576 counts per revolution. But, according to the literature, they are they provided different resolutions to the drive system. Apparently the OSA253 is referred to as a 25,000 count encoder. The 3 means 3 zeros after the 25. The OSA104 is a 100,000 count encoder while the OSA105 is a 1,000,000 count encoder. It is not clear whether the drive scales the 1,048,576 count’s per rev to 25,000, 100,000 and 1,000,000, or whether it is just more convenient to talk in terms of round numbers. However, since there are 20 bits in use, the TI-5000JX provides the count in terms of 1,048,576 count’s per revolution.

The drive can determine which of these encoders is connected to it by the encoder ID.

All of these encoders seem to use basically the same circuit board, so they work virtually identically. The OSA253 and OSA105 do not seem to have the external overheat lines coming into the encoders. In this situation, the overheat inputs are jumpered together on the PCB so that the overheat indication does not go into alarm, when the encoder is removed from the motor. The Data Display for these encoders displays overheat, battery, and internal error bits.

OBE12, OBA13, OSA14, OAH14B, and OSA17 (OSA18) –

The OSA17 is 131,072 counts/rev, OAH14B and OSA14 are both 16,484 counts/rev, the OBA13 is 8,192 counts/rev, and the OBE12 is 4,096 counts/rev. The numerical part of the model number is apparently the number of bits in the count for one revolution. However, the OSA17 and OBA17 encoders have the ability to be programmed as lower resolution encoders. For instance, if a replacement encoder is purchased for an OSA14, it will be an OSA17 (or possibly OSA18). There will typically be a dash number after the OSA17 to indicate this. An OSA17 that has been programmed as an OSA14 will show the encoder ID for the OSA14. If it shows an OSA14 ID, then you should select OSA14 from the list. Always check the encoder ID when testing these encoder and make the selection according to the ID. 

There is a battery bit for the OSA17, OAH14B, OSA14, and OBA13, but there is not even a battery line for the OBE12. It may be that OBA indicates an absolute encoder where battery backup is used, and OBE does not use it. Internal error bits are displayed for all of these except the OAH14B for which an error bit is yet to be identified. None of these encoders show an overheat bit.

OHE4096 –

The OHE4096 is a Nemicon SBC-4096 encoder (there may be other similar Nemicon part numbers ending in 4096, like SBN-4096). Mitsubishi models HA-SH103, HA-LH12K1, and HA-LH102C-L1 are examples of motors that use this encoder. This is basically a 12 bit serial encoder providing 4,096 counts/revolution. It has no multi-turn count and no battery backup. Unlike most serial encoders, it must be indexed before the count is absolute. Rotate the encoder until the INDEX box changes from ALARM to OK in the Data Display. At that time, the mechanical and electrical angles will be active for commutation alignment.

Identification

The encoders whose part numbers begin with OSA or OSE apparently are the removable type encoders. They can be removed in one piece from the motor by removing 4 mounting screws. There is a coupling connecting the encoder shaft to the motor shaft. On most of these encoders, the part number can be seen on a bar code sticker after the encoder is removed. These stickers are often not visible when the encoder is mounted on the motor.

The encoders whose part numbers begin with OBA or OBE apparently are the built-in type encoders. These encoders cannot be removed in one piece from the motor. They must be disassembled from the motor shaft. Usually these encoders can be identified by markings on the large, square IC (integrated circuit) on the encoder PCB which can be seen when the encoder cover is removed. An OBA13 encoder will normally have OBA13 stamped on this IC.

Apparently the OSA17 and OBA17 encoders have the ability to be programmed as other types of encoders. Currently, when a replacement for an OSA14 encoder is purchased, it will be identified as an OSA17 instead of OSA14. In most cases it seems to be identified as OSA17-020. In this situation, the OSA14 selection should be use to read the encoder. In a similar manner, some encoders labeled OBA17 have been found to respond better to the OBA13 selection.

The TI-5000JX now reports an encoder ID field for Mitsubishi serial encoders. This field provides further support in identifying the correct selection to use for various encoders -even ones that may be programmed to work like a different part number. Use this encoder ID field to help verify that you have selected the correct encoder.

Connection

Mitsubishi encoders generally use an MR and MRR (which we sometimes call REQ and REQ*) as the request lines. The drive or tester uses these lines to send the pulse or data code (that tells the encoder to send data) to the encoder. The encoder then can send the requested data back on the MD and MDR (which we sometimes refer to as SD and SD*) as the data lines. This is a typical 4 wire serial encoder system. Some of the older Mitsubishi encoders must use 4 lines in this manner. But, some Mitsubishi encoders also send the data back on the MR and MRR lines. So, it is possible with these encoders to use only 2 wires. For these encoders, sometimes the cables that connect the drive to the encoder will have only 2 lines, (even though the encoders will still usually have all 4 lines). As long as all 4 lines are brought out to the encoder connector, the 4 wire TI-5000JX/TI-3000JX test cables will work. In some cases the MD and MDR lines do not come out from the encoder PCB to the encoder connector. In this situation, the 4 wire test cables will not work.

So far we provide the TI-5658 cable for the only case that we know of where only 2 wires come out on the encoder connector. But, there are probably other cases in existence, and there will probably be more cases coming along in the future. It would be good practice to verify that all 4 wires are coming to the connector – especially if you are experiencing problems in communicating with a Mitsubishi serial encoder.

When we have more motors using 2 wires identified, they will be listed in the manual.

In order to use 2 wire cables, software changes were required for the testers. If you use 2 wire test cables, verify that your tester software version is at the following levels or newer: TI-5000JX V3.4 Beta 16 12/01/10 and TI-3000JX V3.1 Beta19.

Testing

Mitsubishi Incremental encoders are tested as Generic Incremental Encoders using Data Display, Line Levels, Incremental Count Test, and Phase Test for a complete test. Mitsubishi serial encoder types listed above (like most serial encoders) use only the Data Display and the Serial Count Test. The forward armature direction for Mitsubishi motors is CCW looking at the drive shaft end.

Data Display

Data Display is the initial test, and it is started by default when Athena is started. When already in another test, it can be started by clicking on the Data Display button among the test buttons at the top of the display. Use it for the following:

1. Turn the encoder to ensure that the encoder is counting approximately the right number of counts
   per revolution.
2. Use the commutation display to check or set the feedback commutation alignment.
3. Check the encoder status for the following: ensure that the encoder is indexed, communicating properly with the tester, not reporting internal errors, correctly displaying overheat and battery alarms, and displaying the correct encoder ID (if ID is implemented).

The following sections describe information shown on the display.

Commutation

The Fanuc style commutation gray code shown as C1 – C8 and the electrical angle can be used to check and set commutation using a static rotor lockup by applying a small lockup voltage to the stator windings. We strongly recommend using the electrical angle as the superior method of alignment for Mitsubishi encoders. For a particular lockup polarity, the rotor will lock up in as many different positions as there are pole pairs but the gray code and electrical angle indications will be the same at each lockup position. The mechanical angle will be different at each lockup position (except for 2 pole motors where there is only one lockup position), so it is not as convenient to use for feedback alignment. See section 3.2 for a more detailed description of commutation alignment procedures.

The number of poles must be entered correctly for the electrical angle to be correct. The gray code, electrical angle and mechanical angle are derived from the position count. The position count is absolute immediately on power up for Mitsubishi serial encoders.

The table below shows 3 different lockups that can be used to check or set commutation on motors with Mitsubishi serial encoders. The first one puts the feedback on a zero electrical angle which some users favor. It requires applying power to all 3 armature lines.

The last two procedures require applying power to only two armature leads at a time. It is easy to go from +U –V to +U –W just by moving the minus lead from V to W. This should cause the motor to jog 60 electrical degrees in the forward direction (CCW looking at the shaft for Mitsubishi). Failure to move the correct number of degrees or in the correct direction would be an indication of a significant problem. Setting these angles within ±3 electrical degrees is normally quite sufficient.

Count

The Count frame displays the encoder count both as a decimal and hexadecimal number. Users will typically be interested in only the decimal count, but encoder repairmen and other advanced users may find the hexadecimal representation useful. In general this count will not be zero on power up. This is an absolute encoder, and it will remember the count on power up. The number of counts/rev for the various models is shown in the table in an earlier section on types of encoders supported.

Always verify that the encoder count appears to change by the correct number of counts/rev while turning the encoder. If the count is not changing, then there is an encoder problem. As described in a later section, the Count Test may be performed to more accurately determine whether the correct number of counts per revolution is occurring, but this is an important initial evaluation.

Encoder Status

• INDEX – The INDEX box is disabled for all Mitsubishi serial encoders because these encoders display the correct count on power up without indexing.
• DATA - If no data is being sent from the encoder, NONE will be displayed in the DATA box. If the TI-5000JX and the encoder are communicating correctly, RECEIVING will be displayed in the DATA box. The cabling is the first thing to check if the encoder is not communicating, but it can also mean a component failure in the encoder.
• INTERNAL ERROR - The INTERNAL ERROR box will show ALARM if there is an internal error alarm and OK if there is not. The internal alarm is the result of self tests that are done by the encoder electronics.
• BATTERY - The BATTERY box will show ALARM if there is a battery error alarm and OK if there is not. The battery alarm will show when the encoder detects a battery voltage of 2.8VDC or less for some encoders and 3.2VDC or less for others. It is often possible to alternately connect and disconnect battery lines to the encoder to verify that this bit is working properly. Drive literature indicates that 3.6VDC lithium batteries are used. The battery line is brought out near the terminal block on the test cable (see test cable charts in section 2.9 for more info). Connecting a 3.6V source between the line and 0V ground (J1 pin2) should make the display change from ALARM to OK. There is a time constant associated with the battery bit, and the battery voltage may need to be applied for a minute or so before the indication changes. Likewise the battery voltage may need to be removed and the battery input connected to 0V ground for a period of time for the ALARM indication to return.
• OVERHEAT - The OVERHEAT box will show ALARM if there is an overheat error alarm and OK if there is not. This box will be disabled for encoders for which no overheat is detected information, such as the OBA13.
  
  It is often possible to alternately connect and disconnect thermal lines to the encoder to verify that this bit is working properly This field may not be in effect for all serial encoders. Thermal contacts inside the encoder complete a circuit to ground when temperatures are within range. When temperatures become excessive, the contacts open, and the overheat bit is transmitted with the data. Encoders with the circular connectors, such as the OSA104, bring this circuit out on the RED wires (which do not go to the circular connector). In a normal installation these wires are connected through other contacts such as motor overload contacts. These wires can be connected together during testing, and the encoder should not indicate an overheat condition (providing it is not overheated) with OK. If these wires are disconnected from each other, the OVERHEAT box column should indicate ALARM.
• ENCODER ID – Data from Mitsubishi serial encoders contain information that identifies the encoder. When the encoder type detected agrees with the encoder type selected, the ENCODER ID box will show the type detected followed by OK. If they disagree, it will show the type detected followed by Error. In that case, you should change your selection to match the type that is indicated. This is especially helpful when you are testing an OSA17-020 encoder that has been programmed to replace an OSA14. A similar case is an OBA17-052 encoder that has been programmed to look like an OBA13. It can be difficult to make the correct selection without using the ID information.

Count Test

The Count Test can be started by clicking on the Count Test button among the test buttons at the top of the display. The Count Test it will verify that the encoder is incrementing the correct number of counts per revolution. The Count Test for the Mitsubishi encoders is not significantly different from that for other encoders, so please refer to the general information on the count test in Section 2.2.2 for further details. The number of bits tested by the Stuck Bit Test varies depending upon the particular model. Encoders with greater than a 16 bit count per revolution will test bit0 to bit15 for activity. Others will test as many bits as are used in the count for one revolution.