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TCP/IP voltmeter & thermometer  ( measurement over LAN / internet )
TCP/IP voltmeter is DC voltmeter with integrated web server in it. The voltmeter can operate stanalone and doesn't need any additional PC. It has its own IP address so it can be accessed via web browser from any place in the world. The board contains 2- channel Voltmeter, Thermometer and Relay. 

tcp/ip voltmeter
TCP/IP Voltmeter/thermometer
Voltmeter range  :  0 - 50 Volts
Thermometer range  :  -25 C  to +125 C
Relay  :  1A / 120 Volts
Usage : Technical parameters:
Remote measurement of voltage and temperature over LAN/internet. Remote On/Off switch using relay.

Board size :
Voltmeter impedance :
Voltmeter error :
78 x 67 mm
1 MOhtm
0,1 V max

Power suply : + 5V to + 25V from external power supply ( 150 mA/ 5V )

HW configuration : 2 x Voltmeter , 1 x Thermometer , 1 x Relay 

Voltmeter is designed with regard to achieve good electrical parameters with the minimum requirements for hardware. Voltmeter has a high input resistance and very good accuracy of measurement. Thermometer uses external temperature sensor and maesures in the range -25 to +125 C. Relay can switching max. voltage 120 Volts.

Features :
- Complete web server and TCP/IP stack
- DHCP client ( dynamic IP address)
- static or dynamic IP address
- ICMP client ( ping command )
- Dynamic DNS ( DynDNS.org etc...)
- GET and POST command
- telnet
- SNMP agent
- mail sending possibility( SMTP )
- USART connection
- TCP client , TCP server
- Berkeley API ( sockets connection )
- EEPROM webpage storage

TCP/IP voltmeter is based on TCP/IP stack from Microchip.   For TCP/IP voltmeter a  microcontroller PIC18F67J60 is used.

Datasheet to TCP/IP voltmeter : datasheet     Size : 196 kB
Utilities for TCP/IP voltmeter : Utilities     Size : 177 kB
Setting Dynamic DNS : Dynamic DNS     Size : 1.5 MB
Web site
Displaying data in web browser
Measured data are displayed in web browser. Refresh period is 0.5s by default ( can be changed ). Web server uses AJAX technology, so only small ammout of data is transfered. Therefor page refreshing is quite quick. Any known web browswer are supported : Microsoft IE, Firefox, Chrome etc...
Web pages are stored in EEPROM memory and user can modify it. Another way to obtaining data from TCP/IP voltmeter is through telnet , SNMP protocol or TCP client.
web site voltmeter
TCP/IP voltmeter/thermometer features
TCP/IP voltmeter setup.
TCP/IP voltmeter is  plug and play device. After connecting the ethernet cable and power supply is ready for use.
It includes a DHCP client and after connecting to the network, it will obtain dynamic IP address. Static IP address can also be set.
Voltmeter.
For voltage mesurement A/D converter in the microprocesor is used. It's a 10-bit A/D converter with good characteristics. TCP/IP voltmeter has two input channels. Both channels share a common ground.  Before A/D converter is operational amplifier whit high input impedance and good linearity.
Thermometer.
For temperature measurement an external temperature sensor is used. It is very accurate, resolution is 0.1 Celsius.  As the temperature sensor DS 18S20 from Dallas is used. More in Datasheet here. Temperature sensor has 40 cm long cable that connects to the board.
More picture
bottom site bottom site tcp/ip voltmeter inputs thermometer sensor
Another voltmeters.
Another types of voltmeters on this page : USB voltmeter.