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This application note gives an indication of how to use the RFH5xx series in dynamic applications like hanging conveyors.
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RFH5xx
Table of Contents
This application note gives an indication of how to use the RFH5xx series in dynamic applications. Therefore the application note explains, how to calculate the maximum passing speed for the different RFH5xx devices. Also, some sample timings show the performance of these devices.
Calculate read/write time or speed
The calculation of the speed of the transponder depends on the device type (RFH505, RFH510, or RFH515) with the corresponding reading field, the transponder size, and if the UID is read or User Memory is read. This chapter explains these relationships. The passing speed of a transponder is always calculated with the following formula:
Reading field
The reading field width depends on the device (505,510,515) and the used transponder. In the following picture, the reading field of all three RFH5xx devices with different transponders is shown. This information is also available e.g. in the manual, available at sick.com in the product information space.
Timing
The second parameter of the formula is the "read time". This is the time needed for a read or write operation. The time of this depends, if the UID is read or User Memory is read or written. This time is multiplied by two to satisfy the Nyquist-Shannon sampling theorem.
Scan UID mode
In the Scan UID mode, the RFH5xx reads a new UID every 10 ms. so the "read time" is always 10 ms.
Read UMEM
When talking about reading memory blocks, we have to differentiate between transponders, that have 4 Bytes (e.g. NXP ICODE SLIx) or 8 Bytes block size (Fujitsu MB89R118). Note: If always the same part of the memory should be read and it is a time-critical application: please use the Auto-Read Mode (Operation Mode 1). The timings that are shown in the table below, also refer to Auto-Read Mode.
number of blocks / formula
4 byte block size (NXP ICDOE SLIx)
8 byte block size (Fujitsu MB89R118)
1
46 ms
48 ms
2
53 ms
56 ms
3
60 ms
64 ms
formula (valid for one process data format (data requested <=28 Byte))
39 ms + (no of blocks * 7ms)
40 ms + (no of blocks * 8 ms)
General
For dynamic applications the Scan UID Mode is always the first choice, because the cycle time is 10ms. The timings for User Memory are higher (see above table).
Examples
To get a better understanding, see the following examples.
Example 1
A 16mm coin transponder is used with RFH505. The UID should be read. What is the maximum speed?
With the given formula:
and the reading diagramm of the RFH505 with 16mm coin:
So the calculation is: v= 20mm/(2*10ms) = 1 m/s So the maximum speed is 1 m/s for this application.
Example 2
Two blocks User Memory of an Icode SLIx Transponder (4 Byte per block) in coin 16mm should be read with an RFH515 at a speed of 1 m/s. Is this possible?
First the time for reading two blocks à 4 Byte is calculated with the above-shown table. t= 39 ms + (no of blocks * 7ms) = 39ms + 14ms = 53 ms The reading field width for a 16mm coin is 50mm.
The formula v=s/(2*t) can be transformed to: t=s/(2*v). With values: t=50mm/(2*1 m/s)= 25ms So the time of 53ms differs a lot from 25ms. This application could not be solved with this speed.
Application guide
Separation of transponders (e.g. in a hanging conveyor system)
The task is a separation of transponders. The transponders have only a small distance to each other (for example 4mm between two 16mm coins). Such a sample is shown as application 1 in the following figure.
Due to the fact, that the transponders are very close to each other, the best option is to use a reader with a small reading field, so that only one transponder is inside the reading field. If more than one transponder is in the reading field, the RFH5xx would not give out a result, because he is only able to read one transponder in the field at the time.
For such applications: RFH505 is the best choice. The RFH505 has the smallest reading field, so the device can easily separate between two transponders.
Fast passing transponders
Applications, where transponder passes very fast and have several around 10 cm distance to each other, and the UID or the UMEM should be read, RFH510/515 or even RFH620 are the best choices. The reason is the brighter reading field. Because of this, the transponder stays a long time in the reading field, and it is possible to read data. Example application: Tags (16mm disc NXP ICODE) are used, with a distance of 20 cm between the tags (see application 2 in follwing picture)
The first station, 8 Byte UMEM should be read. The table below shows the maximum speed possible with which variant, to get a 100% read rate, when using the Auto-Read Mode (Operation Mode 1).
device
max. velocity
distance from tag to the reader
RFH505
< 0,5 m/s
7-8 mm
RFH510
0,7 m/s
10 mm
RFH515
0,8 m/s
10 mm
RFH620
1m/s
30 mm
In the second station, the UID should be read. In Scan UID Mode (Operation Code 5), a new UID is available every 10ms. The table below shows the maximum speed possible with which variant, to get a 100% read rate.
device
max. velocity
distance from tag to the reader
RFH505
< 0,5 m/s
7-8 mm
RFH510
1 m/s
10 mm
RFH515
1 m/s
10 mm
RFH620
1 m/s
30 mm
To conclude: Use RFH510 or RFH515 for such applications. If you need a bigger reading field, consider using RFH620.
Keywords: RFH5xx, RFH505, RFH510, RFH515, RFH, moving, speed, tag