DBK55

8-Channel Frequency-Input ModuleFeatures• Provides eight frequency-­­measurementchannels• Programmable from 1 Hz to 950 kHz  per channel• Provides frequency resolution to0.00025 Hz• Accommodates low-level, high-level,
or digital inputs• Provides per-channel, user-­configurable
low-pass filters
The DBK55 frequency-input module provides IOtech’s data acquisition systems witheight channels of frequency-measurement­capability. The module measures the input signal’s frequency and converts thefrequency to a voltage, which can then bemeasured by the data acquisition system.
The DBK55’s ­output is read by the dataacquisition system along with any otheranalog channels included in the analog scangroup, allowing easy correlation of readings
from the DBK55 with other test parameters.
The DBK55 is particularly useful for making
RPM measurements in applications such as
automotive testing or the monitoring offlow meters. As many as 32 DBK55s can beconnected to one data acquisition system
for a total of up to 256 channels. The DBK55
accepts low- and high-level ­analog signals,
as well as digital signals.

The DBK55 provides eight frequency inputs
Analog Inputs. The DBK55 accepts ACcoupled analog inputs up to 80V p-p. Eachof its channels is equipped with a low-pass
input filter that is jumper selectable for
100 kHz, 300 Hz, or 30 Hz. The module canaccommodate 1 Hz to 100 kHz ­measurementof signals from 50 mV to 80V p-p.
Digital Inputs. The DBK55’s digital inputs,
which can measure signals from 0.001 Hz
to 950 kHz, feature TTL Schmitt-trigger
levels and can accept DC-coupled signals
from -15V to +15V. The DBK55’s digitalinputs are equipped with pull-up resistors
for use with relays or switches.
Frequency Range. The DBK55 provides
12-bit resolution at any frequency from
1 Hz to 950 kHz. Its software programmable range selection feature allows
you to define minimum and maximum
frequencies for conversion. This range isset on a per-channel basis and can ­extend
over the full range of the card or be­reduced to a frequency difference of 1 Hz
or 1% of the maximum input frequency,

DBK55 Frequency-Input Module Block Diagram+527K OhmDigital.33 µfAnalog

One of eight channels

Selectableattenuator

Low-passfilter

20K Ohm

P1

Ch. 0

12

Ch. 1

12

Ch. 2
Ch. 3
Ch. 4
Ch. 5
Ch. 6
Ch. 7

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measurement

121212DAC

Mux
Channel select12121212

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DBK55Specifications & Ordering Information
Specifications

whichever is greater. For example, you can configure one channel for 59.5 Hz to 60.5 Hz, another for 495 kHz to 500 kHz, andyet another for 1 to 950 kHz. When frequencies from 1 Hz togreater than 500 Hz are measured, a corresponding output voltage is generated 250 to 500 times per second; when frequencies
from 1 Hz to less than 500 Hz are measured, they are updated
once per cycle.

Dimensions:  285 mm W x 220 mm D x 45 mm H (11” x 8.5” x 1.75”)
Weight: 1.13 kg (2.5 lbs)
Operating Temperature:  -30 to +70 ˚CConnector: DB37 male, mates with P1*; BNC c­ onnectors for signal inputs
Number of Channels per Module: 8Maximum Modules per System: 32
Frequency-to-Voltage Ranges: Programmable from 1 Hz to 950 kHz digital;
1 Hz to 100 kHz analog
Accuracy: 0.1%
Temperature Coefficient: 10 ppm for every degree outside the range of 0 to 50 ˚C
Low-Pass Filters: 300 Hz and 30 Hz
Debouncing: off 0.6, 2.5, and 10 ms

Update Rates. Since the DBK55’s resolution is 12 bits regardless of
the range selected, update times vary depending upon the range
selected. For ranges from 1 Hz to the user-defined maximum
upper range boundary, the voltage conversion update will occur
every 2 to 4 ms or the period of the input frequency, whicheveris greater. With a range of 0 to 10 kHz, the DBK55 will update
every 2 to 4 ms. If the range is 0 to 60 Hz, the output will update
every cycle or 16.6 ms. As the conversion range becomes morenarrow—for example, from 49 to 51 Hz—the time to resolve the2 Hz differential to 12-bit resolution increases; in this example,
the conversion time would be ­approximately 59 ms.

Input Characteristics
Low-Level Analog Signals
Minimum: 100 mV guaranteed (50 mV typ)
Maximum: 80V p-p sine wave
Minimum Slew: 5V/s
Hysteresis: 15 mV
Impedance: AC-coupled (0.33 µF), in series with 20 kOhm to ground; seeblock diagram
High-Level Analog Signals
Minimum: 1.25V guaranteed, 0.75V typ
Maximum: 80V p-p sine wave
Minimum Slew: 50V/s
Hysteresis: 250 mV
Impedance: AC-coupled (0.33 µF), in series with20 kOhm to ground
Digital Signals
Input Voltage: -15V to +15V
Threshold Voltage (low): 0.8V typ, 0.5V min
Threshold Voltage (high): 1.6V typ, 2.1V max
Hysteresis: 400 mV min
Pulse Width (high or low): 520 ns min
Input Impedance: 27 kOhm pull-up to +5V in parallel with 50 pF
Power Consumption:  950 mW

Incoming Signal Noise. In addition to its low-pass filter, theDBK55 has a predefined hysteresis level built into each channel;
this helps eliminate false counting caused by high-frequency
noise. A programmable debounce is provided with times of 0.6ms, 2.5 ms, and 10 ms; this is for electromechanical devices suchas switches or relays, which bounce or chatter while switching.
Auto-Calibration. The DBK55 is automatically calibrated upon
initialization to compensate for data acquisition system errors
and to ensure system accuracy.

Ordering Information

Description
8-channel frequency-to-voltage input module

Part No.
DBK55

Accessories & Cables
Rack mount kit
Molded T expansion cable; 2 in.
Molded T expansion cable; 4 in.
Ribbon cable, where x is the number of DBK devices attached

RackDBK3
CA-255-2T
CA-255-4T
CA-37-x

Note: The CA-37-x ribbon cable can also be used in lieu of the CA-255-x
molded T cables.

Product Compatibility✔ LogBook✔ DaqBook✔ DaqLab✔ DaqScan✔ DaqBoard/2000 Series* Attachment to the DaqBoard/2000 Series requires a DBK200, DBK202, DBK203A,DBK209, DBK213, or DBK214

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