Heidenhain Serial Encoders

Overview

The Heidenhain serial encoders listed in the next section are supported by this selection. Heidenhain incremental encoders with A, B, and Z lines should be tested as Generic Incremental encoders. Heidenhain encoders with sine/cosine commutation outputs (like the ERN 1387) are discussed in the section on incremental encoders.

Heidenhain encoders commonly show up on Siemens, Bosch, Baldor and Indramat motors among others. The encoders built for the Indramat MDD series motors are significantly different from the standard Heidenhain encoders, and they are described in the Indramat section. Some Heidenhain encoders feature serial outputs, but all Heidenhain encoders have quadrature incremental outputs as well. All encoders appear to have A and B outputs, but not all include a Z index pulse. When a Z pulse is provided, the incremental part of the encoder can be tested like any other incremental encoder (as described in the incremental section). It is typically the serial encoders that do not include an index pulse, and tips are given in this section for testing the incremental section on those encoders.

The incremental outputs come in several formats: TTL, HTL, 1V p-p sine, and 11 µA p-p sine. The less common 11 µA format is not supported by the TI-5000JX. The 1V p-p sine outputs should be used with the TI-5101 1 V p-p interface module. This module amplifies the 1V p-p signals up to a range near 5 V which is more acceptable to the TI-5000JX. Usually the A and B signals will work without the amplification, but the Z pulse sometimes will not. The TTL signals will work directly just like any other 5 V incremental encoders. The HTL signals should be limited to less than 15 V to avoid over-voltage to the TI-5000JX inputs. When the incremental encoders include commutation, it comes in the form of a C and D, sine and cosine, outputs. These outputs provide one period of a sine or cosine wave for each revolution of the encoder which can be converted to an angle. This angle can be read using the Sin/Cos 1 Period/Rev function by selecting Incremental Encoder, AB Quadrature Count and then selecting Sin/Cos Commutation in the Data Display window. See Section 2.3.5.1.2 for more information on testing these encoders.

The RON3350 and ERN1387 are two such encoders, and the ones used on Siemens 1FT6 motors can be connected to the TI-5000JX using the TI-5010 cable. You can use the TI-5010 cable pin designations as a guide for connecting to other (non-Siemens) motors.

Heidenhain supports two serial data formats: SSI and Endat. The TI-5000JX software is compatible with both formats at this time (as indicated in the next section). In addition to the serial lines, the Endat and SSI encoders also include 1V p-p A and B lines (no index pulse is included).

Types Supported

The following list shows the Heidenhain serial encoders that are either currently supported by the TI-5000JX or are under development and will soon be supported:

These are not serial encoders - test as incremental. May have sine/cosine comm. lines.

Note: Some of the encoders listed above may not be selectable in the current version of software but may be under development. The dash number (-32, -512, -2048) is not shown in the selection box because it is irrelevant to the serial count.

Identification

The Heidenhain encoders are normally clearly marked, so identification is not a problem. Especially for the serial encoders, check the following:

1. For ECN1313 and EQN1325 encoders, check the label to see whether they are SSI or Endat
   format. You will probably see Endat most often, but it can be confusing if it is an SSI and you
   assume it is an Endat.
   
   
2. For ECN413, ECN1313, EQN415 and EQN1325 encoders, check to see whether they are labeled Indramat or have an additional part number that starts with DSF or HSF. These are probably Indramat encoders, and they use a format different from both SSI and Endat. See the Indramat section for more information on these.
   
   
3. The part numbers beginning with EC are single-turn encoders and the EQ numbers are multi-turn
   encoders.
   
   
4. If the third letter is N, such as EQN, the encoder is an optical disk encoder. All of the early Endat encoders had this type of part number. If the third letter is I, they are a magnetic disk encoder. Many of the newer encoders are this type. These encoders may require some type of alignment for the disk in order to work properly, and they may not work properly when unless they are mounted on a motor shaft. Please consult Heidenhain literature for more details.

The TI-5000JX does not currently report an encoder ID field for Endat serial encoders, but this feature is planned for future revisions. The SSI encoders are not known to have ID capability.

Testing

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

1 V p-p Signals –

The 1 V p-p signals must be verified on encoders that incorporate these signals. If the incremental count is not working correctly, that will be an immediate indication of a problem. However, the fact that the incremental count appears to be working is not sufficient. The amplitude of these signals should be checked.

Amplitude measurement is probably best done with an oscilloscope. Connecting the scope ground clip to J1 pin 2 and checking the amplitude of the individual line at J1 pins 3, 4, 5, and 6, is a good method to use. This should be done coming out of the encoder before the signals go through any adapter modules. Since these are nominally 1 V p-p between true and complement lines, each individual signal will be about 0.5 V p-p. Some encoders may provide a 1 V p-p signal on the true lines (pins 3 and 5) and a DC voltage of about 2.5 VDC on the complement lines (pins 4 and 6). But most will provide 0.5 V p-p on all 4 lines.

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

Checking and setting commutation requires knowing the forward armature direction and the number of motor poles. There a several ways to determine those parameters, but here is a simple procedure using static lockups. These procedures are facilitated by using the TI-5260 PM Rotor Lockup Switch.

1. Lock the rotor using a +U –V polarity. Note the TI-5000JX mechanical angle reading.
   
   
2. Switch the minus lead from V to W and note the direction of shaft rotation. That direction is the forward armature direction for the motor.
   
   
3. Note the new mechanical angle reading for the +U –W lockup.
   
   
4. As a double check, determine the number of different positions of rotation in which the rotor locks for the +U –W polarity.
   
   
5. The number of poles can be determined by the number of lockups for a single polarity or the change in mechanical angle when moving from the +U –V to +U –W lockup. The following table summarizes this information:

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. The Fanuc style commutation gray code shown as C1 – C8 can also be used for commutation, but we strongly recommend using the electrical angle as the superior method of alignment for Heidenhain 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 Heidenhain serial encoders.

Siemens -

The table below shows 3 different lockups which can be used to check or set commutation on Siemens motors with Heidenhain 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 (CW looking at the shaft for Siemens). 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.

Bosch and B+R –

The use of Heidenhain serial encoders on Bosch and B+R motors is more complicated than Siemens motors. These motors use the memory provided by the Endat encoders, and they store a commutation offset in the memory. By using the commutation offset, the encoders do not have to be set to a common alignment. Each motor can be aligned differently, and in general they are. If you are familiar with the Indramat digital encoders or Allen Bradley motors with Hiperface encoders, you recognize this scheme. You can use the TI-5000JX to see how the encoder is aligned when you receive the motor, and you can set it back to that alignment after repair, but you cannot verify that that alignment is actually correct without retrieving the commutation information from the encoder memory. Memory Test software that will provide alignment information is currently under development for both of these motors.

Kollmorgen AKM –

We believe that this is the correct alignment for the Kollmorgen AKM motors.

We do not currently have alignment information for Baldor motors using the Endat encoders.

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.

The ECN encoders are single-turn encoders in that they do not keep track of revolutions. The EQN and EQI encoders are multi-turn encoders, and they will keep track of revolutions (typically 4,096 revolutions).

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.

Typically serial encoders that include incremental lines are tested both as incremental encoders and serial encoders. Since the Heidenhain serial encoders do not include an index pulse, an incremental encoder count test cannot be performed. Reading the absolute count from EQN 1325 provides a possible method of also checking the integrity of the incremental count. The procedure is as follows:

1. Read the absolute count from the Data display and write it down.
   
   
2. Click the Select Feedback button and select an incremental encoder with 8192 counts per turn.
   
   
3. Go back to the data display, and it should show a count of zero. Turn the encoder approximately 10
   revolutions, and write down the count.
   
   
4. Select the EQN1325 serial encoder again.
   
   
5. Go back to data display and read the absolute count from the display. Subtract the count recorded in step 1 from this count. It should compare very closely to the count recorded in step 3.

A similar procedure can be used for the ECN 1313, but it is complicated by the fact that the ECN 1313 does not count revolutions. This can be overcome by modifying the above procedure slightly. In step 1, turn the encoder until the absolute count is approximately 1,000. In step 3, turn the encoder 10 1/4 turns clockwise. In step 4, of course, select ECN 1313. In step 5, add 81920 (the count for 10 complete turns) to the absolute reading. This would be the final reading if the ECN 1313 was capable of keeping track of revolutions. Subtracting the count in step 1 from this number should be very close to the count recorded in step 3.

The above example is correct for encoders with 8,192 incremental counts/rev. As shown in the identification table, some Endat encoders have only 128 or 2,048 counts/rev. The procedure above will change accordingly with those numbers.

Encoder Status

INDEX – The INDEX box is disabled for all Heidenhain 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 Pulsecoder.

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. Unlike most other encoders, the Endat encoders latch the errors. That is to say that the INTERNAL ERROR box will continue to show ALARM indefinitely, once an error occurs. Most encoders will no longer show an alarm, if the problem is no longer detected by the encoder.

Apparently there are some events, such as power supply glitch or low supply voltage, that can cause an internal error alarm. However, even after the problem is corrected, the INTERNAL ERROR box continues to show alarm. The TI-5000JX can clear the memory location that latches the error by clicking the Reset Alarm button. If an alarm is cleared in this way, and the error continues to come back (for instance after rotating the encoder, cycling power, or allowing some time); then there is probably a problem with the encoder. If it fails to reappear, it may be that the encoder does not have a problem, and the alarm was caused by some temporary circumstance.

Heidenhain literature indicates that causes for alarms could be position error, illumination, signal amplitude, etc.

ERROR TYPE – The Error Type field will provide a numerical description of the alarm if there is an alarm. The Endat encoders provide a bit pattern that describes the alarm. The Endat documentation shows these possible alarms:

These alarms are reported by the alarm bit pattern. A given encoder may not implement all of these alarms, and there is another bit pattern in the Endat data that indicates which errors are reported for that particular encoder. The TI-5000JX software takes this bit pattern into account and reports only the errors that are implemented for the encoder under test.

More than error one bit may be HI indicating more than one parameter in alarm. In that case the ERROR TYPE box will show the number of each error. For instance, 2 3 would indicate both error 2 – Signal Amplitude and 3 – Position Value errors were reported by the encoder.

ENCODER ID – The ENCODER ID will indicate the type of Endat encoder in use based on information read from the Heidenhain section of the encoder memory. This is base primarily on the number of serial counts/rev and whether or not it is a multi-turn encoder. This information may not allow it to completely

identify the encoder. For instance, it cannot tell the difference between an EQI1325 and an EQN1325. But for the purposes of testing the encoder and alignment, this is not important.

If the ID checking software agrees with your encoder selection, it will indicate OK in the ID box. For instance if you select EQI1329, and the ID agrees with that, the ID box will show ‘EQI1329 OK’. If you have selected the wrong encoder, it will show ‘EQI1329 Error’. In that case, you should verify that you have made the wrong selection and make the correct selection.

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 Heidenhain 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 stuck bit test will test bit0 to bit12 for activity for 8,192 count 13 bit Endat encoders.