Data Delivery Devices VHF, UHF & ISM Wireless RTU RFScada 8ADI-9DO 4ADI-5DO User Manual

							RFScada 8ADI-9DO/4ADI-5DO Manual Ver 3.6 Copyright ©2005 Data Delivery Devices LLC Page - 111 – Bartlesville OK Tel 918-335-3318      FAX 918-398-9990 
Sample Questions and Applications. 
 
900 MHz vs. 2.4 GHz  
It seems that everywhere you look another ‘spread spectrum’ 2.4GHz devices comes out, 
including cordless phones, local wireless computer networks for homes and offices, video 
cameras, video links, toys etc. Isn’t the very popular 2.4GHz frequency band the way to go, 
almost all low cost wireless devices appear to be a 2.4 GHz devices.  
 
For a long range, high reliability product such as the RFScada device the 2.4 GHz band is a 
poor choice. For short range (typically less than fifty feet), generally indoor devices such as 
toys, video links or wireless computer networks the 2.4 GHz band has some advantages, 
such as using a smaller and cheaper antenna than required by 900 MHz devices. Many 
public places like airline terminals, hotels, hospitals, coffee houses, bookstores etc. are 
installing these wireless networks, and so the band has quickly become saturated with these 
devices, especially in urban locations. This often results in interference and poor (or no) 
operation for devices that compete in this frequency range; and many users find that 
additional 2.4GHz devices will not operate satisfactorily in the vicinity of other 2.4 GHz 
devices. The biggest advantages of the 900 MHz ISM band is the greater range (typically at 
least 3 times that of 2.4GHz), reduced attenuation from rain when compared to 2.4GHz 
devices and lower power consumption. The 900 MHz ISM band is the best choice for license 
free devices such as the RFScada products, which are designed for the highest reliability, 
interference rejection and longest range in hostile, industrial environments.  
  
Cordless Phone 
I have a ‘spread spectrum’ cordless phone at the house, it does not operate more than 100 
feet from the base station and it certainly does not work ¼ mile away. I understand that 
certain versions of the RFScada devices are also ‘spread spectrum’, how can they operate 1, 
5 or even 40 miles away? 
The main reason is power. The term ‘spread spectrum’ covers a general method of 
transmission, where transmit and receive frequencies are constantly changing or ‘hopping’ 
through various channels. This method was devised as a means to allow many devices to 
effectively share a bandwidth. There are several classifications allowed by the FCC to cover 
different devices and applications, these classifications also govern both the RF power and 
antenna systems that may be used. These classifications all use the generic term ’spread 
spectrum’ as a transmission method. The FCC designates your cordless phone and similar 
consumer devices as a ‘portable device’ with a severely limited RF power output and 
antenna. The RFScada is not designated in this group, and therefore may transmit both with 
a much higher power (up to 1 Watt in the 902-928 MHz ISM band) plus it may also use an 
FCC approved directional antenna that provides more system power gain in certain 
directions. In fact, because of the higher RF power output emitted by the RFScada unit the 
FCC mandates that it must maintain a separation distance of at least 20 cm (about 8 inches) 
to any nearby persons. 
 
True Range 
The range is mentioned as 0.25, 5 and 40 miles etc. What is the real range? 
This is a very difficult question to answer, since it will vary in every installation. The actual 
range will depend on many factors, including the device location, height, shape of the terrain, 
terrain surface, obstacles, the antenna used, proximity to similar devices, radio model etc. As 
a very general guideline in a typical, outdoor location, using the lowest power radio option  
						

							RFScada 8ADI-9DO/4ADI-5DO Manual Ver 3.6 Copyright ©2005 Data Delivery Devices LLC Page - 112 – Bartlesville OK Tel 918-335-3318      FAX 918-398-9990 
available (-SS), where each RFScada unit may be visible from the other and using the 
internal antennas supplied with the standard product a range of at least two miles is to be 
expected, and five miles is usually possible. A similar ‘line of sight’ installation, using the 
optional 13 dB gain Yagi antennas at each end should produce a range of 25 miles with the  -
SS version, 40 miles using the -SS1 version. Using the internal antenna and inside a typical 
factory, with moving and stationary machines, obstacles, metal walls, interfering devices and 
no line of sight the range may be reduced to a few hundred yards with ISM devices. The VHF 
and UHF models have much better coverage in non line of sight applications, plus have 
higher RF power output so coverage with those models is substantially higher. The range 
depends on many factors. Please consult with the factory for your specific application; If you 
are unsure of the best model for your application please call the factory for application 
assistance. If the exact site locations (GPS co-ordinates) are know a suitable solution may be 
recommended using topology programs at Data Delivery Devices LLC. Evaluation units may 
be available for testing at your location.     
 
Separate Transmitter and Receiver. 
I ordered a transmitter for my tank and receiver for the well control. There appears to have 
been a mistake as both units look to be identical. Shouldn’t one be a transmitter and one a 
receiver?  
The units are identical (except for any options that may be installed). Every unit is both 
a transmitter and a receiver. This is the only way that units are able to positively verify correct 
operation of all other units. The units continually communicate with each other to ensure 
constant and valid data exchange. If for some reason a unit needs to be replaced (for 
instance it may be been damaged or stolen) then another standard unit may replace it. 
  
System Data Verification 
How do I know that the output data I receive is valid and is not interference from another 
device?  
There are many levels of sophisticated data encryption and protection incorporated in the 
device. Lets follow a typical signal to see what actually happens. First of all analog and digital 
input data is collected at each unit. The data is encrypted in a  format that incorporates a 
constantly changing rolling code and is then mixed with other data pertinent to the unit, such 
as the local DC voltage. A 16-bit cyclic redundancy check (CRC) value is then calculated for 
this coded data and added. Now the encrypted plus CRC coded data is passed to the RF 
section and transmitted using 25 constantly changing frequencies and using yet another, 
completely independent 16-bit CRC with a different algorithm from the first.  
The remote unit receives the RF data and verifies that the 16-bit RF CRC is correct. It 
then further analyzes the received data and verifies that it also passes the second CRC 
encryption check. The remote unit then analyzes the transmitted data plus other information 
from the first unit. If the data is addressed to this unit it responds, then removes from this 
dual-verified data any information it needs. Finally this data is used to update the state of the 
outputs, to faithfully reflect any output states sent to it from the first unit. Any ‘single bit’ error 
in the whole process will result in an unverified data packet, and that data will be completely 
ignored. If ‘correct and double verified’ data does not arrive at a receiver within a (user 
programmable) time delay the unit will extinguish the ‘COMMS OK’ status LED, set the 
‘system ok’ relay output to inactive, and set all analog and digital outs to the default, off state. 
After good data has been received at one unit it will repeat the whole process by transmitting 
its own input states to the other units in a similar manner. Units will complete the whole cycle 
(input/encrypt, transmit data, receive data, decrypt, update outputs) several times a second to  
						

							RFScada 8ADI-9DO/4ADI-5DO Manual Ver 3.6 Copyright ©2005 Data Delivery Devices LLC Page - 113 – Bartlesville OK Tel 918-335-3318      FAX 918-398-9990 
insure that the output data is valid. If any unit fails for any reason then all outputs change on 
all units to the default (off) state within a few seconds, the default setting is 10 seconds but it 
is user programmable for each unit.       
 
 
Functional Integrity and Verification 
We want to replace some competitors units that have poor range and marginal performance. 
Also, since we now realize the competitors units we own are just ‘one way’ devices we have 
actually been using two complete sets of them for each signal monitored, as we need to verify 
that they are actually functioning - data integrity is very important for this application. With the 
RFScada units is there a way to tell if the remote unit is receiving my signal correctly? 
Yes, there is full data verification. Unlike competitors ‘one way’ or ‘report on an event’ type 
these maintain continuous communication and are fully bi-directional so there are several 
ways to verify full and correct data transfer. Since all units are identical with built in 
transmitters and receivers it is easy to verify reception of data remotely. First of all, by the 
very nature of the device if the two on board transmit and receive status LED’s are quickly 
flashing (normal operation) the devices are both exchanging good, verified data. Secondly the 
‘system status’ LED and relay (connector J11) will be active all the time that all of the devices 
are maintaining a verified data exchange.  When communication is interrupted at any unit and 
for any reason the ‘system status’ LED and relay will become inactive within seconds of the 
interruption. If this unit is communicating correctly the LED will slowly flash and the relay will 
toggle slowly, indicating a problem on another unit. It is therefore possible to tell, from any 
unit, the status of every unit in the system. Finally, if required it is possible to manually verify 
complete operation of any units. Take an unused output of the remote unit and directly 
connect it to an unused input on the remote unit. At the ‘local’ unit close (short together) the 
input. This will cause the second output of the remote unit to close, which is now directly 
wired to another input on the remote unit. This state of input two will now be transmitted back 
to the ‘local’ unit by the remote. Therefore, providing both units are functioning and 
communicating changing the state of the ‘local’ unit input will cause the monitored output at 
the local unit to also change, all within a second. This verifies, in order, full local data input, 
encryption, local RF transmission, remote RF reception, remote decryption, remote output, 
remote input, remote encryption, remote RF transmission, local RF reception, local 
decryption, local verification and local output all within a few seconds.      
 
AC Power Loss and Generator Operation 
Our remote unit is powered from a generator that automatically starts and runs for a couple of 
hours then stops for a few minutes. The remote unit is successfully monitoring the tank level, 
and continues to operate correctly when the generator is stopped, powered by the generators 
battery. Is it possible to also monitor when the generator is running? 
Yes. Simply connect a 115 VAC relay coil across the generators 115 VAC output; connect 
the relays normally open contacts to any unused digital input to continually indicate the 
running status of the generator. If you have a computer connected via Modbus to the local 
RFScada device it is also possible to monitor the generators DC battery Voltage.     
        
Interference between Multiple Units 
We have a pair of RFScada units that have been operating flawlessly for some time. We now 
need another pair but they will be located within a couple of miles from the first. Will two pairs 
of RFScada interfere with each other?  
						

							RFScada 8ADI-9DO/4ADI-5DO Manual Ver 3.6 Copyright ©2005 Data Delivery Devices LLC Page - 114 – Bartlesville OK Tel 918-335-3318      FAX 918-398-9990 
Each system of up to 32 units are matched together for transmission and reception. There 
are seven sets of identity that the units may have, so up to seven pairs of units may all 
operate in close proximity so long as they all have different id’s. When supplied the standard 
units are configured for set ‘0’, but they can be configured at the factory for ‘6’ to ‘6’. A record 
is kept of the units supplied for each customer, so when ordering additional units please 
advise if you need a replacement for a damaged one or a unit to operate on a different 
frequency set. There are solutions offered for applications where more than seven pairs are 
required to operate, or systems where there is a single ‘base’ master unit and multiple slave 
units, please consult the factory for further details.  
 
Rain Attenuation 
Here in the jungle we often experience heavy rain. Does it affect operational range? 
Heavy rain does have an affect on the range, but it is generally negligible. It attenuates 
the signal by approximately 0.2dB per mile for a torrential storm, which means a range 
difference of less than a few feet per mile. 
 
Pampered Horses 
We train and stable many valuable horses for clients on a large ranch. For security reasons 
we have just installed an electrically operated locking gate restricting access to the property. 
The gate is powered by a solar panel and 12 Volt battery since it is remote from any source of 
power. It also came with remote controls from the manufacturer that allow us to operate it 
from our vehicles when we are within 50 feet or so, but they will not operate from our main 
office which although visible from the gate is almost a mile away. We have considered 
purchasing additional remotes for staff to use, but we also have many frequent visitors and 
deliveries. If the gate is not staffed we install a sign that advises visitors to sound their horn 
on arrival, whoever is closest drives down by the gate and opens it. This most undignified 
entry method is obviously not acceptable for us, our clients or the horses that may be startled 
by the noise. The gate opener has a provision for a manual switch to allow anyone to operate 
the gate, but we have not installed that since it defeats the purpose of having the gate for 
security. The only other option available is a keypad by the gate with a code to enter, but 
again it is not suitable for our many visitors and vendors. We would also like to be alerted 
when the gate is operated so we may monitor activity. The gate installation companies we 
have contacted all have just one possible solution left for us - digging a trench for over two 
miles around the lake and across the beautifully landscaped grounds, then installing a cable 
connected to the gate switch; allowing us to operate the gate from the office. This ‘solution’ 
would be very disruptive to our operations, very expensive, we would not know when vehicles 
with remotes came or left and our clients would still be sitting in their vehicles honking the 
horn to gain entry. Can the RFScada solve any of these problems? 
Yes, the RFScada can solve all of your problems. Here is how to do it. Install one unit at 
the office powered by the standard AC line. Connect a normally open push button switch to 
‘digital input one’, this will be used to allow gate operation from the office. Connect an 
indicator light or alarm indicator such as a bell wired to use the relay one normally open 
contacts. Install the other (we will call it gate unit) by the gate control. The gate unit may be 
powered directly from the 12 volts DC supplied by the gate control battery and solar panel 
since its current draw is small. Connect the normally open contacts from relay one to the 
‘manual operation’ switch input on the gate control. When the push button is pressed in the 
office the gate will operate. Now to solve the next problem, alerting office personnel when a 
guest arrives. A switch may be installed by the gate connected to digital input one on the gate 
unit. When visitors arrive they may press this button, which in turn will activate the alarm at  
						

							RFScada 8ADI-9DO/4ADI-5DO Manual Ver 3.6 Copyright ©2005 Data Delivery Devices LLC Page - 115 – Bartlesville OK Tel 918-335-3318      FAX 918-398-9990 
the office. When the office personnel have verified the guest’s identity they may operate the 
gate from the office. 
Rather than having guests press a button by the gate another option is to use a 
motion/proximity detector or ‘breaking beam’ type detector ahead of the gate connected to 
digital input one. This detector could be situated a short distance before the gate to provide 
an alarm at the office before the guest arrived, minimizing any delay. As an added measure 
of security the second unused input to the gate unit may be wired closed, or even better 
connected to a tamper switch or a switch active when the gate was positively locked. Due to 
this the office unit would have relay output two active all the time under normal 
circumstances, so another alarm (or it could be wired in parallel with the first alarm) would be 
connected to the relay two normally closed contacts. If the secure, continuous data 
communication between the office and gate units were disrupted for any reason, including the 
gate battery failing, cut wires, theft, vandalism etc. then relay two at the office would change 
state alerting the office personnel. 
The complete arrangement at the gate may be repeated at additional gates,  without 
requiring additional units in the office, allowing complete, distributed security control from a 
central point – all without wires. The RFScada provides a complete, secure and cost effective 
solution that adds additional benefits without requiring extensive digging, disgruntled clients 
or frightened horses.             
 
Medical Applications 
We have some medical equipment that may be able to utilize RFScada units. Are they 
suitable for this for application?  
No, they are not. The RFScada units are not authorized nor intended for life support or 
medical applications. 
 
FCC License 
Our old SCADA system radio modem & RTU combination has failed again and we would like 
to replace it with two RFScada units. Do we need to convert our present FCC license to use 
the RFScada devices?. 
No need. No license is required to own or operate the RFScada devices within the USA, 
and the FCC already approves them. Save the renewal fees and throw away your old FCC 
license along with the failed SCADA system.     
 
Solar Panel Operation 
 Can I just connect a 12 volt solar panel directly to the RFScada and operate the unit without 
AC power? 
No, at least not at night. However, the RFScada may easily be operated from a solar 
panel if suitable components are used. First of all a panel must be selected that can supply 
several times the energy required to operate the RFScada (approximately one to two watts), 
since the panel must both supply the unit and be capable of charging the battery in the 
shortest daylight available, even on a cloudy day. A system using a panel having a nominal 
10 or 20 watts output should have an ample safety margin. Secondly a battery or batteries 
must be selected that will be able to hold enough energy to operate the RFScada for a period 
of time, plus the battery must be able to withstand the sometimes fairly heavy charging and 
discharge cycle. Small auto or marine ‘deep cycle’ type batteries are most commonly used, 
as they are universally available at a very reasonable cost. Finally, as mentioned earlier it is 
possible to damage batteries by overcharging them, so some type of charge controller is  
						

							RFScada 8ADI-9DO/4ADI-5DO Manual Ver 3.6 Copyright ©2005 Data Delivery Devices LLC Page - 116 – Bartlesville OK Tel 918-335-3318      FAX 918-398-9990 
normally required. Some solar panels have the charge controller already built in, if that type 
of panel is used another controller is not needed.  
The components required will vary depending on the location, for example Alaska in 
winter has very little daylight available, so a solar system there would need much greater 
capacity than one located in Arizona. It is usually possible to connect the RFScada directly to 
an existing 12 or 24 Volt solar power system that is being used to power other equipment 
such as RTU’s or transducers, simply connect the external source to the DC input.  
 
Cabinet Construction 
The brochure states that the RFScada has a corrosion resistant NEMA 4X rated cabinet but 
the antenna is located inside. Doesn’t the stainless steel cabinet severely restrict the unit’s 
range? 
No, the corrosion resistant NEMA 4X rated cabinet is not stainless steel but made from 
fiberglass with stainless steel fittings (hinge, locking latch etc.) so it has very little effect on 
the signal.      
 
Mounting Inside Steel Enclosure 
If the unit is mounted inside a steel electrical switchboard will the range be affected? 
If using internal antennas yes, the range will be reduced if it is mounted inside a steel 
enclosure. Whether the attenuation will be enough to prevent operation will depend on the 
cabinet, distance to the other unit and all the other factors that affect range. If mounting inside 
a steel enclosure an external antenna may extend the range significantly.