Introduction

The Hohner Wireless system consists of a battery pack, a transmitter, the encoder and the receiver module.  The transmitter is built onto the encoder and the battery pack can be replaced in the 'hot' zone by anyone.  The photo below shows in detail the components.

Pretty much, the power is 'wireless' and intrinsically safe, unlike current systems on the market where you still have to power the system with wires...which defeats the whole purpose...or if they are battery powered, the battery is way to big and cumbersome, and zone 1 certified only instead of zone 0, and can NOT be hot-swapped.

The battery pack and encoder and transmitter are all certified to Ex ia IIC standards.

IECEX (IECEx SIR 08-0015X) certificate

ATEX (SIRA 08ATEX2054X) certificate

Data Transmission

Encoder to Receiver is 2.4 GHz.  Proprietary data transmission.

Data rate is 250 kbs

Peak RF output is 0dBm, about 1mW

Receiver to Controller output is Hardware:  RS232, Quadrature or 4...20 mA

Possible protocols can be ASCII, ModBus, ProfiBus, DeviceNet

Data Output Speed per Type of Sensors

Incremental Encoder: Data packet (set of pulses) every 16ms

Absolute Encoder: 1 position every 20 seconds

Multiturn Encoder: 1 position every 60 seconds

Fuel sensor: 1 reading every 60 seconds

These speeds and formats are for about 5 year battery life for 24/7 use, and will be standard.  If data has to be read more frequently and quicker, the battery life will go down accordingly.  It is very easy for us to do, just a couple of lines in C++, so do not hesitate to ask.

Data Security

Secure data transmission - signal is checked 3 times

1. Receiver recognizes only this signal with a product specific code

2. Data is transmitted with a checksum and verified in the receiver

3. 2.4 GHZ base frequency is product specific and has 1 MHz bandwidth in 124 possible channels

A wrong data transmission is not possible.  A data transmission can be missed - this has the effect that updating is delayed since the un-transmitted data is stored within the transmitter until a succesful transmission has occurred, which in turn sends current data plus the back log of data.

If the sensor loses power or there is a fault with the sensor, our electronics will detect this since we allow a maximum time out period of 5 minutes up to an hour (depending on the sensor used and application) along with the receiver module sending a signal (ping) to the sensors to check it's status.

Battery Details

We use a lithium thyonide battery with 19,000 mA hours.  Life time is dependant on the application and number of transmissions per second, though about 5 years is average for 24/7 use.  Another way to determine this is the theoretical 1 billion data transmissions possible.

We have a long term test going on in house, at a rate of 30 transmissions per second and the device has been functioning since August 2011, that comes out to 1 billion data transmissions!  Which means, that so far, the battery lasts longer than the theory.