Stegmann Serial Encoders – Mitchell Electronics Inc

Overview

The Stegmann serial encoders listed in the next section are supported by this selection. Stegmann incremental encoders with A, B, and Z lines should be tested as Generic Incremental encoders. Stegmann encoders used on Indramat digital motors are discussed in the Indramat section. This section deals with Stegmann Hiperface and SSI encoders.

The Stegmann AG100 SSI encoder is used on Indramat MAC motors. The AG661 SSI encoder is used on Siemens 1FT5 series motors. The Stegmann SSI encoders are similar to SSI format encoders from other manufacturers such as Heidenhain and Hengstler. They use clock and data lines, and there are no incremental lines.

The newer Stegmann Hiperface encoders are showing up on many brands of motors including Allen Bradley, Baumuller, Berger Lahr (Telemechanique), Control Techniques, Elau, Modicon, Octacom, Rexroth, and SEW Eurodrive to name a few. While the details are different, the Hiperface encoders are similar in function to the Heidenhain Endat encoders. There are serial lines for accessing absolute position data and memory data, and they use analog 1V p-p sine and cosine signals that can be counted like A and B quadrature lines. Also like the Endat encoders, there is no index pulse. Without an index pulse, in order to obtain absolute position information from the incremental count (from the 1V p-p lines), the incremental count must first be referenced to absolute position data read from the serial lines. Tips are given in later sections for testing the incremental section on these encoders.

Some Hiperface encoders are specified to operate from 5 VDC, but others are specified in the 7VDC to 12 VDC range. Since even the 5VDC versions will accept up to 12 VDC, it is recommended that the TI-5104 Adapter Module, which provides 8 VDC, be used with the Stegmann Hiperface encoders (Caution: Always check the rating listed on the encoder label to verify the range!). The 8VDC output is within the correct range for all Hiperface encoders that we have encountered. The TI-5104 also provides the additional advantage of amplifying the 1V p-p sine outputs from the incremental lines.

The SNS50 and SNS60 encoders are a peculiar variation in the Hiperface encoders. They are so different from the other Hiperface encoders that there is a special section describing them at the end of the Stegmann section. Be sure to read this section if you encounter one of these encoders. These encoders are used on AB 8720 series spindle motors and on Fagor PM brushless motors.

Types Supported

The following list shows the Stegmann serial encoders that are currently supported by the TI-5000JX, and it lists some representative motors on which they are used as well as test cable possibilities.

Please check the current PDF catalog file and price list files for a complete listing of all cables supporting motors using Stegmann encoders.

In addition to the above encoders, a DSL-3J08G0M2XB9, which apparently is a 5V SKM36 encoder, is sometimes used on MPL-A1XX motors. It is not clear whether this is an AB part number or Stegmann. But, the encoder seems to test fine using the SKM36 selection.

Note: The first count is the number of counts/rev for the incremental signals, the second is the number of counts/rev for the absolute serial position count, and the last count is the number of revolutions that can be counted (for multi-turn encoders only).

Identification

The Stegmann encoders are normally clearly marked, so identification is not a problem. The TI-5000JX does currently report an encoder ID field for Hiperface serial encoders, and this will help assure that the correct selection has been made. The SSI encoders are not known to have ID capability.

Connection

Connection requires using the correct cable as shown in the chart in the Type Supported section. Also the Athena ‘Feedback Selection’ frame has a cable dropdown menu from which you can select the cable that you need. After making the cable selection, that selection will appear on the Data Display report which is helpful in documenting the cable used.

The TI-5069 generic cable connects directly to the 8 pin connector on the encoder, so it should work with all Hiperface encoders. Download cable sheets from the Customer Page at http://www.mitchell electronics.com for cable pinouts and wiring details. Cable configurations other than the cables listed are known to exist. There may be cables that are made by OEM machine manufacturers using these encoders.

If properly cabled, the Stegmann Hiperface encoders can be used with the TI-5104 Adapter Module so that it is easier to check the incremental portion with the same connection. See the section on cables for more information.

Testing

Stegmann incremental encoders are tested as Generic Incremental Encoders using Data Display, Line Levels, Incremental Count Test, and Phase Test for a complete test. Stegmann serial encoder types listed above (like most serial encoders) use only the Data Display, Serial Count Test and Memory Test if they have memory.

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. The Hiperface encoders will 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).

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:

Turn the encoder to ensure that the encoder is counting approximately the right number of counts per revolution.
Use the commutation display to check or set the feedback commutation alignment.
Check the encoder status for the following: ensure that the encoder is communicating properly with
the tester, not reporting internal errors, and displaying the correct encoder ID.

The following sections describe information shown on the display.

Commutation

The electrical angle is best for checking and setting commutation. For a particular lockup polarity, the rotor will lock up in as many different positions as there are pole pairs, but the 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 electrical angle and mechanical angle are derived from the position count. The position count is absolute immediately on power up for Stegmann Hiperface and SSI serial encoders. Some Indramat MAC and Siemens motors use the Stegmann SSI encoders for positioning. These motors use Hall effects for motor commutation, so the encoder does not need to be aligned for commutation purposes.

The method of alignment for Hiperface encoders will vary with motor manufacturer. The table below shows 2 different lockups that can be used to check or set commutation on Allen Bradley motors with Hiperface serial encoders.

The 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 Allen Bradley). 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.

Unlike most feedback alignment discussed in this manual, Allen Bradley MPL, MPF and 1326 motors using Hiperface encoders do not have a common lockup angle, and in general, they will all lock up at different angles. These motors store a commutation offset in the encoder memory. By using the commutation offset, the encoders do not have to be set to a common alignment. In order to correctly check or set the alignment, you have to run the Memory Test on the encoder, and write down the +U –V and +U –W lockup angles provided by the memory test.

Count

As mentioned previously, the Hiperface encoder provides an incremental count using the 1V p-p analog signals. This count is shown in the Incremental Count frame. This count may be zeroed at any time by pressing the Zero Count button. The SSI encoders do not provide an incremental count.

The Revolution and Position Count frame displays the absolute position count as a decimal number in the POS COUNT box. This count will range from 0 to counts/rev -1. Multi-turn encoders will provide a revolutions count as a decimal number in the REV COUNT box. This box is disabled for single-turn encoders. The HEX COUNT box will display, in hexadecimal format, the position count (for single-turn encoders) and a composite position and revolutions count (where the revolution LSB is the next bit above the MSB of the position count for multi-turn encoders). Most users will be interested only in the decimal count, but encoder repairmen and other advanced users may find the hexadecimal representation useful. In general the absolute count numbers will not be zero on power up. Because it is an absolute encoder, 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.

As an example of single and multi-turn model numbers, the SRS50/60 encoders are single-turn encoders in that they do not keep track of revolutions. The SRM50/60 encoders are multi-turn encoders, and they will keep track of 4,096 revolutions. The “S” and “M” in the names designate single and multi-turn respectively.

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 Stegmann Hiperface serial encoders do not include an index pulse, an incremental encoder count test cannot be performed. Comparing the incremental count with the absolute count provides a possible method of also checking the integrity of the incremental count. The procedure is as follows:

Move the shaft until the absolute position count in the POS COUNT box reads 0.
Click the Zero Count button to force the incremental count to 0.
Turn the encoder 10 revolutions. With multi-turn encoders, you can use the data in the REV COUNT box to keep track, but you will just have to count revolutions for single-turn encoders.
Adjust the shaft to get as close as possible to 0 in the POS COUNT box.
Write down the incremental count in the INCREMENTAL box. It should be very close to 10 times the number of incremental counts/rev.

Encoder Status

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. There is no good way to determine whether data is being received from the Stegmann SSI encoders, so the DATA box is not implemented for those selections.
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. Stegmann literature lists the causes for alarms which are detailed in the following discussion of error type.
ERROR TYPE – When the Hiperface encoder produces an internal alarm, a code indicating the cause of the alarm may be read from the encoder. This code is displayed for Hiperface encoder alarms. For other types of encoders, the error type is displayed if it is known. The following list of errors applies to the Hiperface encoders:
ENCODER ID – The ENCODER ID will indicate the type of Hiperface encoder in use based on the ID code read from the encoder. This box will be disabled for other types of encoders that do not provide ID data.

If the ID checking software agrees with your encoder selection, it will indicate OK in the ID box. For instance if you select SRS50, and the ID agrees with that, the ID box will show ‘SRS50 OK’. If you have selected the wrong encoder, it will show ‘SRS50 Error’. In that case, you should verify that you have made the wrong selection and make the correct selection.

Memory Status

The Read Memory Status button on the Data Display allows the user to check whether memory is currently in use for a particular encoder. Clicking the button when connected to an SRM50 encoder on an Allen Bradley MPL motor would produce the following display:

This tells us that there are 4 memory fields of 32 bytes each defined in this encoder. All 4 fields are write enabled (WE). The access code is set to 0 (could be 0, 1, 2, or 3). The code enable bit (CE) is not set for the 4 defined fields, so the access code does not have to be used. The total bytes number of memory bytes used is 128. The total bytes unused is 0, and this means that all of the available memory is in use. No more data fields could be defined for this memory because it is used up.

This data formatting is done by the motor manufacturer and is of little concern to the TI-5000JX user. However, it is useful to look at it to verify that the memory looks normal. For instance if you see that no fields have been defined for an encoder on an Allen Bradley MPL motor, it is very likely that the encoder has been replaced and the correct data has not been programmed into the memory. This would be very important to know because the motor would not run correctly on the Allen Bradley drive. It is also useful to check on unfamiliar motors to determine whether the motor manufacturer is using the memory.

This Memory Status data is automatically included on the Data Display report when a Stegmann Hiperface encoder has been selected.

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. This will run a standard Count Test on the absolute position count. The incremental count must be tested as described previously. The Count Test will verify that the encoder is incrementing the correct number of counts per revolution. The Count Test for the Stegmann 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 bit13 for activity for 16,384 count encoders and bit0 to bit14 for activity for 32,768 count encoders. As with all serial encoders, there will be some error shown in the Count Test. The slow data rate from the Hiperface encoders will make the errors somewhat larger than typical serial encoders. Turning the encoders very slowly will help reduce the errors.

Memory Test

See the section for the appropriate motor brand. The memory test data is very specific to the particular motor.

SNS50/60

The Stegmann Hiperface SNS encoders are quite a bit different from the other Hiperface encoders. Here is a list of their peculiarities:

These encoders provide serial data lines, like other Hiperface encoders, but they do not provide absolute position information from the serial data. All position data is from the A and B (cosine and sine) channels.
As with other Hiperface encoders, memory data may be read from the serial lines, but memory is not defined by the user as with other Hiperface encoders. The same amount of memory is always defined, and some of the memory is used by Stegmann to provide calibration information for the encoder signals.
On power up, the A and B channels will provide a resolution of 4,096 counts/rev using 1024 periods of cosine and sine waves.
Using the serial lines, the encoder may be programmed to output one period of sine and cosine signals per revolution somewhat similar to a single speed resolver (ignoring the excitation) or the C and D channels of an Heidenhain ERN1387 encoder. The serial lines can be used to program the encoder back to 1024 periods per revolution.
The serial lines may be used to program the encoder to output an index pulse once per revolution. In this mode, the encoder can provide absolute position data (after it is indexed), and it works like any other incremental encoder with A, B, and Z channels. The index pulse uses the serial lines, so in this mode the serial channel can no longer be used for serial data. The encoder will remain in this mode until it is powered down.

Cable Connections-

The SNS encoders are compatible with the TI-5069 cable that connects directly to Stegmann Hiperface encoder 8 pin connectors. The cable should be modified so that terminal block pin 7 is jumpered to pin 9 and pin 8 is jumpered to pin 10. This connects the index channel which apparently only exists on the SNS50/60 encoders. Any other Stegmann cables that would be correct for specific motors (such as the TI-5064 for Allen Bradley) would also need this modification.

Testing the Encoder –

Since this encoder has several different modes, and since you can’t come back out of the Z pulse mode (without cycling the power), it is best if you proceed through this checkout in a specific order. It may also depend on what type of motor is using the encoder as to how important some steps may be.

For example, some motors may not use the memory, so the memory test may not be important in those cases. At this time, the memory test can only interpret the data format for the Allen Bradley Spindle motors. Data from other motors will not look like good data when the TI-5000JX system tries to interpret it as Allen Bradley data.

A spindle motor that is an induction motor, rather than permanent magnet brushless, may not make use of the one period per revolution sine waves or the index pulse. However, unless you are sure a certain function of the motor is not used, you should try to check it out.

Suggested Test Sequence –

The following sequence will work well in most cases:

Connect the encoder to the TI-5000JX using the appropriate Stegmann cable and the TI-5104 Adapter Module.
Note: The cable used should be modified so that the index pulse on the serial channel gets to the Z
pulse input of the tester. This means that pins 7, 9, and 11 should be in common with each other and pins 8, 10, and 12 should be in common with each other.
Select the Stegmann SNS Hiperface encoder.
In the Data Display, the Encoder ID box should say SNS OK. That means that it has read the SNS encoder ID from the serial lines, and it is telling you that you have selected the correct encoder. Obviously this also tells you that the serial lines are functional and that you are receiving data from the encoder. The normal box for indicating receiving data is not functional for the SNS encoder.

The INTERNAL ERROR box should say OK. If it says ALARM, it will also display a 2 digit hexcode describing the alarm. A code of FF usually means that it is not sending any data. This could mean anything from a cabling problem to a bad encoder.

When you turn the encoder (or motor) shaft CW (facing the shaft), the Count should increment and decrement when turn CCW. Remember that this is not absolute position data and cannot be used for alignment. The mechanical and electrical angle boxes will contain dashes because the data is not absolute.
The motor is an Allen Bradley and, if you have the Allen Bradley memory options, you can click on the Memory Test button to perform a memory test. The memory data will be displayed, and you can check for correct checksum results. If it is not an Allen Bradley motor, the data displayed will be meaningless. However, in either case, you can click the Save Encoder Data File button to save the data to your hard drive.
Click on the Data Display button to return to the Data Display. Click on the Sin/Cos Commutation radio button, and the display should change to the sin/cos display. The individual cosine and sine readings are displayed as well as the A and B channel differential voltages that caused them.

There will now be data in the mechanical and electrical angle boxes because the sin/cos signals produce absolute position data. You can record static lockup rotor angles if the motor is a permanent magnet brushless type. You must set the POLES selection to the correct number of poles, and for documentation purposes, you should set the LOCKUP selection to the voltage polarity that you are using for the lockup. These angles will be similar to the angles you will get using the 4096 count, but they will not be exact. In order to get more exact results form the sine/cosine, the correction data from the memory must be used. The software does not currently make corrections using this data.
Click on the 4096 Count/Rev radio button to go back to the incremental mode. Again the angles boxes will contain dashes because the position data is not absolute. Click on the Enable Z Pulse button so that the encoder will begin providing an index pulse. Several of the boxes will become disabled, and the INDEX box will be come enabled and probably show ALARM. Rotate the shaft until the INDEX box changes to OK. This will mean that you have indexed the encoder. If this does not occur after turning an entire revolution, you may have a problem with the encoder or cabling.

When the encoder is indexed, the angle boxes will again show data because the incremental channels are now providing absolute data. This data can be used to check or set alignment by static lockup of the rotor if the motor is a permanent magnet brushless type. You must set the POLES selection to the correct number of poles, and for documentation purposes, you should set the LOCKUP selection to the voltage polarity that you are using for the lockup.

This data should agree pretty closely with the data taken from the sin/cos mode. This data should be more accurate because the 4096 counts/rev provides more resolution.
Once the index pulse is enabled, a standard Count Test may be performed on the encoder. Click on the Count Test button and perform the Count Test in the normal manner.
You can further check the A, B and Z channels by looking at them with a scope. Connect a scope with the ground clip on J1 pin 2 and the probe on J1 pin 3 (coming into the TI-5104 Adapter module). Connect the other channel probe to pin 4. On pin 4 you should see about 2.5V DC. When you turn the encoder, you should see about 1.0V p-p. This voltage should go approximately 0.5V above and below the DC voltage on pin 4. Repeat the process looking at a DC voltage on pin 6 and a 1.0 V p-p signal on pin 5. Once per revolution you can see the index pulse on the scope. Apparently it is a full sized 5 V signal rather than 1V p-p.