Measurement WBK30 User Manual

WBK17

Counter-Input Module with Quadrature Encoder Support

For use with WaveBook/516, /512A, /516A, and /516E

Description ……1
Hardware Setup ……3

Configuration ……3
Power …… 3
Using Fastener Panels to Stack Modules …… 4

Functional Concepts ……4

Input Coupling ……4
Analog Filtering ……5
Comparator ……6
Debounce Module ……7
Terms Applicable to Counter Modes…….11
Counter Options ……11
Counter/Totalize Mode ……12
Period Mode ……14
Pulsewidth Mode ……17
Timing Mode ……19
Encoder Mode ……20
Digital Inputs ……29
Digital Outputs…… 30
Pattern Detection and Data Markers ……31

Software Support ……31
Fuse Replacement ……36
WBK17 - Specifications …… 37

Description

Front Panel

Rear Panel

Front Panel

Rear Panel

WBK17 Modules – Showing Front and Rear Panels

Counter Input - snap-in terminal blocks. Includes connections for Common, Low, & High for each of 8 channels.
Power Out [for Encoders] snap-in terminal block. Includes connections for Common, +5 VDC, and +15 VDC.
Digital Expansion In (HD26 Female) & Digital Expansion Out / Digital In, Trigger, Clock (DB25 Female)
LED Indicators - Active, Ready, and Power

Power Switch
Power In and Out (DIN5 connectors) for +10 VDC to +30 VDC
Digital Outputs - snap-in terminal block with connection for Common and 8 Channels

Expansion Control In (DB15 Male) & Expansion Control Out (DB15 Female)
Expansion Signal In (BNC) & Expansion Signal Out (BNC)

WBK17, Counter/Encoder Module

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WBK17, pg. 1

The WBK17 is an 8-channel multi-function counter/encoder module that can be used with WaveBook/516,
/512A, /516A, and /516E systems. The WBK17 module can not be used with earlier WaveBook models
such as WaveBook/512 and WaveBook/512H.

Each of the high-speed, 32-bit counter channels can be configured for counter, period, pulse width, time
between edges, or encoder modes.

All channels are capable of measuring analog inputs that are digitized by the WaveBook at up to
1 MHz. The Analog Waveform Input Mode can be used to measure waveforms from 0 to 100 V peak-to­peak (±50 V). The maximum analog over-range is 150 V peak-to-peak (± 75 V). The resolution is:

0.002307 V/bit.

WBK17, pg. 2

WBK17 Block Diagram

The WBK17 can be used with any combination of up to 7 additional WBK signal-conditioning modules.
Together these modules can measure a broad range of signal types and address a broad range of
applications.

A discussion of the following items is presented in Functional Concepts, which immediately follows

Hardware Setup

AC/DC Coupling

•

Analog Filtering

•

Comparator

•

Debounce Circuit

•

Counter Options

•

Digital Inputs

•

Digital Outputs with Pattern Detection

•

.

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WBK17, Counter/Encoder Module

Hardware Setup

Configuration

All WBK17 configurations are controlled by software. The WBK17 requires no hardware settings.

Power

Reference Notes:

Encoder setups for WBK17 applications begin on page 22 of this document module.

➣

Refer to the WaveBook User’s Manual (p/n 489-0901) in regard to power, expansion

➣

control, and expansion signal connections.

When using WaveView you will need to set several parameters so WaveView can best

➣

meet your application requirements. For software information, refer to the

WaveBook User’s Manual

(p/n 489-0901).

Power In

Power Out

[to the WBK17]

The WBK17 can be powered by an included AC power adapter or from any +10 to +30 VDC source, such
as a car battery. Check the WBK17 specifications for current requirements. For portable or field
applications, the WBK17 and the WaveBook can be powered by the DBK30A Battery Module or the
DBK34 UPS/Battery Module. Both devices contain rechargeable battery packs. The
Manual (p/n 489-0901) includes details.

[to the Encoders]

The WBK17 provides output power of +5V at 1A, and +15V at 500 mA to supply power to encoders.
Power connections from the WBK17 to [up to 4] encoders are made on the snap-in screw terminal block
located on the WBK17’s front panel. Example wiring diagrams for encoders begin on page 23.

You must compute power consumption for your entire system. You may need to use
auxiliary or high-current power supplies. The WaveBook User’s Manual
(p/n 489-0901) includes tables for calculating system power requirements and
discusses power supply options.

Reference Notes:

The

➣

➣

WaveBook User’s Manual

power requirements and discusses power supply options.

Encoder wiring diagrams are included in the Encoder section of functional concepts.
These drawings begin on page 23.

(p/n 489-0901) provides tables for calculating system

WaveBook User’s

CE Kit

WBK17, Counter/Encoder Module

If your WBK17 is to be part of a CE compliant system, you will need to use part
number WBK17-CE KIT. The kit includes the terminal block headers and cable
housings that are needed to cover exposed sections of connectors and wiring, thus
bringing your WBK17 up to meet or exceed CE standards.

For a list of applicable CE Safety and EMC standards, as well as the CE Compliant
Operating Conditions that have been specified for WBK17, refer to the WBK17
Declaration of Conformity, p/n 1064-0740.

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WBK17, pg. 3

Using Fastener Panels to Stack Modules

For convenient mounting, the WBK17 has the same footprint as other WBK modules and WaveBooks.
Fastener Panels, sometimes referred to as “splice plates,” provide a means of stacking WaveBooks and
modules. Optional screw-on handles are available for portable applications. Refer to this manual’s
introduction for assembly information.

When using WBK17 modules in conjunction with other WBK modules, the WBK17
modules must be located closest to the WaveBook due to the CA-217 cable length.
The order of the other WBK modules does not matter.

Fastener panels will partially block the vents on WBK16s and the vents on
WaveBook/512A, /516, /516A, and /516E when the units are stacked.
This partial blocking of vents does not jeopardize the cooling process.

Functional Concepts

Input Coupling

Each WBK17 channel has a programmable input coupling feature. Input coupling can be turned off, or be
selected for AC or DC coupling. The type of coupling is determined after the input differential amplifier.
DC coupling makes use of the path going straight to the filter stage (of the programmable analog filter),
where as AC coupling makes use of the path with the 1 uF capacitor.

The inclusion [or exclusion]of DC offsets is important when calculating the appropriate comparator
threshold for the input waveform.

Use AC coupling to reject unwanted DC offsets. In other words, to prevent DC offsets from reaching the
comparator. AC coupling works well when the input is constantly changing. If the input stops for longer
than one second, it will appear as DC and may cause the comparator to switch on the decaying DC input.

Use DC coupling when both AC and DC components are to be presented as input to the comparator.
DC coupling does not reject anything. If the input can have periods of stability longer than one second, use
DC coupling so the comparator does not switch on a decaying DC input.

Input Coupling

WBK17, pg. 4

The input coupling stage, shown in the figure above, is compatible with encoder outputs that have balanced
outputs (driving both high and low.) The high and low voltages are required to be within the maximum
input voltage range of –75V to +75V. A wide range of input waveforms can be accommodated since the
WBK17’s comparator threshold can be set anywhere from –12.5V to +12.5V. Many encoders offer
line driver outputs, using 4469 or 8830 driver circuits. The 8830 is a dual differential line driver with
balanced TTL outputs capable of directly driving long lengths of coax or twisted pair cable. The 4469 is a

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WBK17, Counter/Encoder Module

CMOS output driver with high current outputs used with voltages of up to 15 V. Balanced line drivers that
are used at higher voltages (e.g., +15 V and +24 V) and used in differential mode are particularly immune
to external noise sources.

Some encoder outputs will be open-collector type. These require a pullup resistor in order to operate. In
many cases, the pullup resistor is already incorporated inside the encoder, other times it must be supplied
externally. Since the “open-collector with pullup resistor” output is inherently unbalanced (drives strongly
in the low direction, weakly in the high direction) the input differential amplifier will distort the input
waveform. This distortion can be easily viewed when the input channel is scanned by the WaveBook. This
distortion may have to be taken into account when setting the comparator threshold. Many times the best
way to accommodate unbalanced inputs is to AC couple and set the threshold at 0.00V. This forces the
comparator to trigger on the center of the waveform, where the input has high slew and little noise. An
option is to DC couple and set the comparator threshold at the mid-point of the transition.

If external pullup resistors are required, they can be connected at the WBK17’s input terminal blocks.
A pullup resistor can be placed between any input channel and one of the two power supplies offered on the
output power connector (+5V and +15V.) Choose a pullup resistor value based on the encoder’s output
drive capability and the input impedance of the WBK17. Lower values of pullup resistors will cause less
distortion but also cause the encoder’s output driver to pull down with more current. Although the WBK17
has a wide input dynamic range and good common-mode rejection, you should connect the encoder GND to
the COM input, when possible.

Analog Filtering

Each channel has a single-pole, low-pass filter with three programmable cut-off frequencies.
These are: 100 kHz, 20 kHz, and 30 Hz.

Use analog filtering to reject low-level noise that may otherwise interfere with the comparator. The analog
filters are most beneficial when the unwanted noise is far outside the desired bandwidth. For example, if the
desired input bandwidth is only 0 to 10 kHz, then the 20 kHz low pass filter will reduce unwanted noise
components of 20 kHz by 3dB. Unwanted noise of 200 kHz will be reduced by 23dB; and noise
components of 2 MHz will be reduced by 43dB.

Since the analog filters come before the comparator circuit and the expansion analog output path, their
effects will be observed at the comparator and in the analog waveform scanned by the WaveBook.
The analog expansion path going back to the WaveBook has a 450 kHz single pole filter.

WBK17, Counter/Encoder Module

Analog Filter

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WBK17, pg. 5

Comparator

Each channel has its own individually programmable comparator as shown in the figure below. The output
of the filter stage feeds the comparator circuit. The analog waveform that is present at the comparator is
gain adjusted and then multiplexed onto the WaveBook’s analog expansion port. This allows the analog
input waveform (as it appears at the comparator, post coupling, post filter) to be scanned like any other
analog waveform. The analog path going to the WaveBook is bandwidth-limited to 450 kHz. The analog
path between the input and the comparator is not bandwidth-limited unless a low-pass filter is used.

Comparator

The comparator has a programmable threshold, set by the DAC. The threshold can be set anywhere from
–12.5V to +12.5V in 100mV steps, referred to input. Since the counter output and analog waveform can
be scanned together, the effects of different comparator switching thresholds can be easily observed. This
allows easy adjustment of the comparator-switching threshold based on input waveform characteristics such
as noise and ringing.

The following diagram shows two common input waveforms: a square wave that has some ringing and a
sine wave. The comparator threshold should be set so that the ringing on the square wave does not cause
extraneous switching of the comparator, causing false counts to be measured. Ideally, the comparator
threshold should be set so that the comparator switches at the point of fastest slew rate on the input
waveform. This occurs in the grayed regions of the waveforms.

Amplitude modulated noise may also cause false switching of the comparator. The effects of amplitude
modulated noise can be minimized by setting the threshold at the point of fastest slew rate on the input
waveform. The sine wave shown below has its fastest slew rate within the gray region.

Set the comparator threshold within the gray regions to avoid the effects of ringing and noise.

WBK17, pg. 6

Setting the Comparator Threshold

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WBK17, Counter/Encoder Module

Debounce Module

Each channel’s comparator output can be debounced with 16 programmable debounce times from
500 ns to 25.5 ms. The debounce module eliminates switch-induced transients typically associated with
electro-mechanical devices including relays, proximity switches, and encoders.

From the following illustration we can see that there are two debounce modes, as well as a debounce
bypass. In addition, the signal from the comparator can be inverted before it enters the debounce circuitry.
The inverter is used to make the input rising-edge or falling-edge sensitive.

Edge selection is available with or without debounce. In this case the debounce time setting is ignored and
the input signal goes straight from the inverter [or inverter bypass] to the counter module.

There are 16 different debounce times. In either debounce mode, the debounce time selected determines
how fast the signal can change and still be recognized.

The two debounce modes are “trigger after stable” and “trigger before stable.” A discussion of the two
modes follows.

Debounce Model

WBK17, Counter/Encoder Module

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WBK17, pg. 7

Trigger After Stable Mode

In the “Trigger After Stable” mode, the output of the debounce module will not change state until a period
of stability has been achieved. This means that the input has an edge and then must be stable for a period of
time equal to the debounce time.

Debounce Module – Trigger After Stable Mode

The following time periods (T1 through T5) pertain to the above drawing. In Trigger After Stable mode, the
input signal to the debounce module is required to have a period of stability after an incoming edge, in order
for that edge to be accepted (passed through to the counter module.) The debounce time for this example is
equal to T2 and T5.

T1 – In the example above, the input signal goes high at the beginning of time period T1 but never stays

high for a period of time equal to the debounce time setting (equal to T2 for this example.)

T2 – At the end of time period T2, the input signal has transitioned high and stayed there for the required

amount of time, therefore the output transitions high. If the Input signal never stabilized in the high
state long enough, no transition would have appeared on the output and the entire disturbance on the
input would have been rejected.

T3 – During time period T3 the input signal remained steady. No change in output is seen.

T4 – During time period T4, the input signal has more disturbances and does not stabilize in any state long

enough. No change in the output is seen.

T5 – At the end of time period T5, the input signal has transitioned low and stayed there for the required

amount of time, therefore the output goes low.

WBK17, pg. 8

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WBK17, Counter/Encoder Module

Trigger Before Stable Mode

In the “Trigger Before Stable” mode, the output of the debounce module immediately changes state, but
will not change state again until a period of stability has passed. For this reason the mode can be used to
detect glitches.

Debounce Module – Trigger Before Stable Mode

The following time periods (T1 through T6) pertain to the above drawing.

T1 – In the illustrated example, the Input signal is low for the debounce time (equal to T1); therefore when

the input edge arrives at the end of time period T1 it is accepted and the Output (of the debounce
module) goes high. Note that a period of stability must precede the edge in order for the edge to be
accepted.

T2 – During time period T2, the input signal is not stable for a length of time equal to T1 (the debounce

time setting for this example.) Therefore, the output stays “high” and does not change state during
time period T2.

T3 – During time period T3, the input signal is stable for a time period equal to T1, meeting the debounce

T4 – At anytime during time period T4, the input can change state. When this happens, the output will also

T5 – During time period T5, the input signal again has disturbances that cause the input to not meet the

T6 – After time period T6, the input signal has been stable for the debounce time and therefore any edge on

Mode Comparison

The following example shows how the two modes interpret the same input signal (which exhibits glitches).
Notice that the
mode. Use the

requirement. The output is held at the high state. This is the same state as the input.

change state. At the end of time period T4, the input changes state, going low, and the output follows
this action [by going low].

debounce time requirement. The output does not change state.

the input after time period T6 will be immediately reflected in the output of the debounce module.

Trigger Before Stable

option to achieve maximum glitch recognition.

bypass

mode will recognize more glitches than the

Trigger After Stable

WBK17, Counter/Encoder Module

Example of Two Debounce Modes Interpreting the Same Signal

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WBK17, pg. 9

Debounce times should be set according to the amount of instability expected in the input signal. Setting a
debounce time that is too short may result in unwanted glitches clocking the counter. Setting a debounce
time too long may result in an input signal being rejected entirely. Some experimentation may be required
to find the appropriate debounce time for a particular application.

To see the effects of different debounce time settings, simply view the analog waveform along with the
counter output.

Use trigger before stable mode when the input signal has groups of glitches and each group is to be counted
as one. The trigger before stable mode will recognize and count the first glitch within a group but reject the
subsequent glitches within the group if the debounce time is set accordingly. The debounce time should be
set to encompass one entire group of glitches as shown in the following diagram.

Trigger after stable mode behaves more like a traditional debounce function: rejecting glitches and only
passing state transitions after a required period of stability. Trigger after stable mode is used with electro­mechanical devices like encoders and mechanical switches to reject switch bounce and disturbances due to
a vibrating encoder that is not otherwise moving. The debounce time should be set short enough to accept
the desired input pulse but longer than the period of the undesired disturbance as shown in the diagram
below.

WBK17, pg. 10

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WBK17, Counter/Encoder Module

Terms Applicable to Counter Modes

The following terms and definitions are provided as an aid to understanding counter modes.

Detection Signal:

channel has an associated detection signal (Detect 1 for Channel 1, Detect 2 for Channel 2, etc.) A
channel’s detection signal will go active high when that channel’s counter value meets the setpoint criteria
programmed into the pattern detection module. Detection signals can be scanned along with any other
channel in the scan group.

Gating:

will be allowed to count, when the mapped channel is low, the counter will not count but hold its value.

Any counter can be gated by the mapped channel. When the mapped channel is high, the counter

Mapped Channel:

counter module. The mapped channel can participate with the channel’s input signal by gating the counter,
clearing the counter, etc. The 16 possible choices for the mapped channel are the 8 input signals (post
debounce) and the 8 detection signals.

Start of Scan:

group and therefore pulses once every scan period. It can be used to clear the counters and latch the counter
value into the acquisition stream.

Terminal Count:

the terminal count: 65,535 for a 16-bit counter (Counter Low); and 4,294,967,295 for a 32-bit counter
(Counter High). The terminal count can be used to stop the counter from rolling over to zero.

Ticksize:

20000ns. For measurements that require a timebase reference like period or pulsewidth, the ticksize is the
basic unit of time. The count value returned in the scan is the number of ticks that make up the time
measurement.

The ticksize is a fundamental unit of time and has four possible settings: 20ns, 200ns, 2000ns,

A detection signal is one of 8 outputs of the pattern detection module. Each input

A mapped channel is one of 16 signals that can get multiplexed into a channel’s

The start of scan is a signal that is internal to the WBK17. It signals the start of a scan

This signal is generated by the counter value. There are only two possible values for

Counter Options

The following mode options are available with the WBK17 and are detailed in the upcoming pages.
A separate block diagram has been created for each mode. Note that the OPT numbers relate to
sections of the block diagrams.

Counter/Totalize Mode

Period Mode

Pulsewidth Mode

(see page 12):

OPT0: Selects totalize or clear on read mode.
OPT1: Determines if the counter is to rollover or “stop at the top.”
OPT2: Determines whether the counter is 16-bits (Counter Low); or 32-bits (Counter High).
OPT3: Determines which signal latches the counter outputs into the data stream back to the

WaveBook. Start of scan or mapped channel.

OPT4: Allows the mapped channel to gate the counter.
OPT5: Allows the mapped channel to decrement the counter.
OPT6: Allows the mapped channel to increment the counter.

(see page 14):

OPT[1:0]: Determines the number of periods to time, per measurement (1, 10, 100, 1000).
OPT2: Determines whether the period is to be measured with a 16-bit (Counter Low);

or 32-bit (Counter High).

OPT4: Allows the mapped channel to gate the counter.
OPT6: Allows the mapped channel to be measured for periods.

(see page 17):

OPT2: Determines whether the pulsewidth is to be measured with a 16-bit counter (Counter Low);
or a 32-bit counter (Counter High).

OPT4: Allows the mapped channel to gate the counter.
OPT6: Allows the mapped channel to be measured for pulsewidth.

WBK17, Counter/Encoder Module

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WBK17, pg. 11

Timing Mode

OPT2: Determines whether the time is to be measured with a 16-bit counter (Counter Low);

(see page 19).

or a 32-bit counter (Counter High).

Encoder Mode

OPT[1:0]: Determines the encoder measurement mode: 1X, 2X, or 4X.
OPT2: Determines whether the counter is 16-bits (Counter Low); or 32-bits (Counter High).
OPT3: Determines which signal latches the counter outputs into the data stream going back to the

WaveBook. Start of scan or mapped channel.

OPT4: Allows the mapped channel to gate the counter.
OPT5: Allows the mapped channel to clear the counter for Z reference.

Counter/Totalize Mode

The counter mode allows basic use of a 32-bit counter. While in this mode, the channel’s input can only
increment the counter upward. When used as a 16-bit counter (Counter Low), one channel can be scanned
at the 1MHz rate. When used as a 32-bit counter (Counter High), two sample times are used to return the
full 32-bit result. Therefore a 32-bit counter can only be sampled at a 500kHz maximum rate. If only the
upper 16 bits of a 32-bit counter are desired then that upper word can be acquired at the 1MHz rate.

The first scan of an acquisition always zeroes all counters. It is usual for all counter outputs to be latched at
the beginning of each scan; however, there is an option to change this. A second channel, referred to as the

“mapped” channel, can be used to latch the counter output. The mapped channel can also be used to:

gate the counter

•

increment the counter

•

decrement the counter

•

The mapped channel can be any of the eight input channels (post-debounce), or any of the eight detection
signals. Each channel has its own detection signal that goes active when any of the sixteen counter value
setpoints has been reached. A detailed explanation of pattern detection begins on page 31 of this document
module.

(see page 20).

WBK17, pg. 12

Counter/Totalize Mode

An explanation of the various counter options, depicted in the previous figure, follows.

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WBK17, Counter/Encoder Module