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General |
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1. |
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What are the
differences between industrial and commercial-grade converters?
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Just as there are many differences
between industrial- and commercial-grade computers, the industrial-
and commercial-grade converters differ in many ways, such as the
level of circuit protection, temperature range and noise tolerance.
Most importantly, true industrial-grade converters, such as
CommFront's, require rugged
components and reliability-engineering designs to withstand heat,
vibration, shock and other environmental factors, therefore, they
are much more durable
than commercial-grade
converters. Industrial-grade converters are designed to interface
with mission-critical equipment, such as computers, PLC, SCADA and HMI - whether in the field, server room, factory, control room, or
fire command center. Visit
the wikipedia's pages for more information on:
Temperature classifications and
Reliability engineering |
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2. |
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Why is it important
to get products certified?
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CommFront products are strictly certified by
SGS/TUV, which
are the
Nationally Recognized Testing Laboratories (NRTLs) in North
America and the Notified Bodies in European Union, the most
meticulous and recognized certifying labs in the industry. This
makes our products safe and reliable for interfacing to
mission-critical devices.
Read more... |
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How to build a
reliable RS485/RS422 network?
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An RS485/RS422 network consists of many different components,
such as cables, RS232/RS485/RS422 devices (master and slaves),
converters, and power supplies, and because this type of
network is normally
used over a long distance and in an electrically noisy
environment, noises, reflections, and data errors might
occur. Building a reliable RS485/RS422 network by choosing the
correct cables, designs, and converters could save a lot of
valuable engineering time and make the system free of the
above-mentioned problems.
Read more... |
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RS485/RS422
Topology: How to connect RS485/RS422 devices?
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RS485/RS422 is a
network in a linear, multi-drop configuration;
however, star-wiring is inevitable in some
places. Our RS485 Hub/Splitter
(Model:
HUB-485-4) splits an RS485 network into four, thus making star-wiring possible. |
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RS485/RS422
Cabling: What cables are recommended?
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Screened twisted-pair cable (e.g. CAT-5e) is recommended to prevent
external noises induced to the RS485/RS422 buses. |
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RS485/RS422
Distance: Maximum distance and how to extend it?
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A single RS485/RS422
loop can go up to 4000ft (1200m) by using standard copper wire (screened twisted pair
such as CAT-5e).
This
distance (using copper wire) can be extended to another 4000ft
(1200m) by using our RS485/RS422 repeater
(Model:
RPT-485_422-2 and
RPT-485_422-4). Note:
A maximum of two repeaters can be used in
series. The RS485/RS422 distance can be further
extended to up to 24.8 miles (40km) by using Single-Mode Fiber Optic
Cables and our Single-Mode RS232/RS485/RS422 to Fiber Optic Media
converter (Model:
FBR-Serial-2). |
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RS485/RS422
Termination (120-Ohm): Why is it important and when to use it?
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RS485/RS422 network is normally used over a long distance and in
an electrically noisy environment, noises, reflections, and data
errors might occur if there is no termination on the RS485/RS422
buses. Both ends of the transmission
lines should be terminated to reduce noises and reflections that can
cause data errors. There are several methods of terminating data
lines, and we recommend parallel termination. Instead of using pull-up or pull-down resistors, the
parallel 120-Ohm end-of-line terminators provide a
hassle-free and effective way of termination. However, since the Terminator
will increase the load on the data circuit, we recommend to turn ON
the Terminator only when the data rate is over 19.2kbps or the distance exceeds 660 feet (200m).
Note: CommFront's built-in 120-Ohm terminators can be easily turned ON or OFF through a simple jumper
setting, thus making our converters ideal solutions for all types of
installations. |
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8. |
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How to turn ON or
OFF the 120-Ohm terminator?
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If you are using
our port-powered converters with the provided terminal blocks, the
120-ohm terminator is set through a simple jumper setting
(marked as "120" for CVT-485-x and "J4" for CVT-485_422-x or
CVT-422-x). Terminate the jumper to turn ON the terminator and
remove it to turn the terminator OFF.
If you are using
our port-powered converters without the provided terminal blocks,
short pin 6 & 7 for CVT-485-x or pin 4 & 8 for CVT-485_422-x /
CVT-422-x on the DB-9 connectors (RS-485 side) to turn ON the
terminator.
For
CVT-485_422-4, tie J3 & J4 to turn ON the terminator for RS485; tie
J1 & J2 to turn ON the terminator for RS422. |
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What is
Opto-Isolation? What are the benefits of using Opto-Isolated
Converters?
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Opto-isolation uses optical isolators to
isolate two serial devices. Optical isolator is a common element
used for RS232, RS485 and
RS422 systems. With an optical isolator, only light passes between
two serial devices, this is performed with an LED and a
photosensitive transistor.
There are many benefits of using opto-isolated converters, most
importantly, it protects your RS232 devices from
transient
surges, lightning and spikes.
Optical isolation also eliminates ground loop and noise problems
because the ground of two connected devices are separated. |
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What is a Static
Protection Circuit? Is it an Opto-Isolator?
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The Static Protection Circuit is also
called an ESD (Electro-Static Discharge). The charged capacitance of
a human body enables a person to destroy integrated circuits with a
single touch. Such a contact can easily occur during the
installation of an interface cable. To prevent ESD damage, our
converters come with the protection circuit to protect against ESD levels for up to ±15kV.
Static Protection Circuit is NOT an
Opto-Isolator. To prevent your
PC or serial devices from being damaged by
ground
loops, transient surges, lightning and spikes,
opto-isolated converters (i.e. CVT-485-3, CVT-485_422-3) or
isolators (i.e. CVT-232A-3 or CVT-232B-3) are required. |
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What is
Auto-Turnaround?
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Auto-turnaround is applicable for 2-wire half-duplex RS485
communication. Upon
sensing a "start bit" (a logic high "Mark" to low "Space"
transition) from its RS232 data transmit line (TxD), the
RS-485 transceiver circuit will change the data direction
automatically so that the RS-485 side is at the "listening"
mode, thus reducing the chance of data collusion.
Auto-turnaround feature is very useful for half-duplex RS485
communications, however, it is not applicable for
full-duplex communications such as RS-232, RS-422 and TTL
because both of the TX and RX channels are operating
simultaneously. |
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What is Balanced
signaling and what is Unbalanced signaling?
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Balanced signaling (also named as
Differential signaling) is used for RS485, RS422, USB and Ethernet,
it is a method of transmitting data by means of two complementary
signals sent on two separate wires. The receiving device reads the
difference between the two signals and ignores the wires' voltages
with respect to ground, therefore, the signal can be transmitted
much longer than its opposite technique: Unbalanced signaling.
Unbalanced signaling (also named as
Single-Ended signaling) is used for RS232 and TTL, the transmitter
generates a single voltage that the receiver compares with a fixed
reference voltage, both relative to a common ground connection
shared by both ends. Unbalanced signaling can not run over a long
distance and might have ground loop and noise problems. |
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What is SMT? What
are the benefits of using SMT circuitry?
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SMT stands for Surface Mount Technology.
Our converters use SMT circuits, thus the current consumption is
very small (less than 10mA), while other Discrete Component type of
converters on the market consume much more power - normally between
50mA to 100mA. Less current generates less heat, hence, the
converters last longer. |
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What is GND? Can I
connect it to the Earth?
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GND on the converters is the Signal Ground. Do NOT connect GND to the
Earth. |
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Can I use your
port-powered converters without the terminal block?
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No problem. For your convenience, we
provide a terminal block with each converter, which is useful as you
can connect the RS-485/RS-422 cables directly into the terminal
block without making your own connector.
You can also use the converters without the terminal block, as it is
merely a conversion from DB9 to Screw Terminals, with some jumpers
on the circuit board. In case you need to make you own connections
without using the terminal block, please refer to the Pin Assignment
on the datasheet for detailed connections. |
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Do I need to set
the baud rate on the converters for them to work?
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This is not necessary, all of our
converters can auto-detect and self-adjust to the data format (baud
rate, data bit, parity, stop bit, etc.) used by the serial devices.
The baud rate, data bit, parity, stop bit etc must be consistent on
the master and slave devices on a higher protocol level. |
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Can I plug / unplug the
converters while they are being used?
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Yes, all of our converters are
hot-pluggable. They are equipped with Data
Transceiver Protection Circuitry to protect the devices from voltage
and current surges. |
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What is the current
consumption of your converters?
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Our port powered converters consume
less than 10mA of current. Our externally powered converters consume
less than 30mA of current, which is about 3 Watts.
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Will the
port-powered converters work with new computers?
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Yes, our port-powered converters work
well with new computers that come with the RS232 ports, which
normally come with a minimum of +/-5VDC port power. However, please
note that most of modern computers (especially laptops) do NOT come with RS232
COM ports, therefore USB to RS232 cables / converters (which
creates a Virtual COM port on the PC) are widely used. |
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Will the converters
work with USB to RS-232 cables/converters?
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We have tested our converters with many kinds of USB to RS-232
cables / converters available on the market. There is no problem
using our converters with USB to RS-232 cables / converters.
However, if you found your USB/RS232 converters/cables do not work
with our converters, please drop us an email. |
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