Water meter system consists of:
• Water meter, IC card and wireless
• Intermediate
• Concentrator (GPRS modem)
• Computer
• Card reader/writer
• Computer online with card reader/writer to be put in bank, house center, shopping center, bus station for convenience to re-charge
Introduction of Zigbee:
Zigbee was introduced by IEEE Personal Area Network (PAN) workgroup on Nov. 2001. It is the IEEE 802.15.4 technical standard. Zigbee is the commercial name of IEEE 802.15.4. ‘Zigbee’ comes from the bee’s Z shape jumping to inform mates, and exchange information.
Zigbee features:
1. Low power. 2 AA batteries can last 6-24 months or even longer time; while bluetooth can last several weeks, WiFi several hours.
2. Low cost. Simple protocol brings about simple controller, and Zigbee is free of patent.
3. Low speed. 50Kbps (2.4GHz), 40Kbps (915MHz), 20Kbps (868MHz)
4. Short distance. 10-100m, 1-3km after adding RF transmitting power.
5. Short active time. 15ms from sleeping to wakeup, 30ms connect to net, while blueteeth 3-10s, WiFi 3s.
6. High capacity. one concentrator for 60.000 meters.
7. High level safety.
8. Free frequency. ISM 430-440MHz(China), 915MHz(USA), 868MHz(Europe), 2.4GHz(world)
Zigbee we used:
. Working Frequency: 2.40-2.48GHz
. Band: 80M
. Channel: 16
. Channel capacity: 5M
. Modulation: DSSS
. Free ISM
. Standard: 802.15.4
Advantages of our system:
1. Recharge mode:
a) the card record total amount or total volume when recharge;
b) insert card to the meter, meter read the new total amount or total volume of the card. Remaining amount or volume = total amount or total volume – total using by the meter.
c) No more worry about card copy.
2. Recharge unit: amount or volume.
unit of amount: unit of currency
unit of volume: cubic meter
3. Price changes can be programmed very easily.
4. Installation: the Zigbee system makes the meter enter into the system automatically. Installation is the same as that of normal meter, but no need to record meter serial number. Much easier job.