Design and manufacture of a 4-20mA & 3k NTC sensor interface
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Description
Experience Level: Intermediate
I need a sensor interface designing and manufacturing as follows:
Two channels - 1no 4-20mA current loop and 1no 3k NTC thermistor.
Must be battery powered (12v) and be able to enter a quiescent state to conserve battery power.
Must have regulated 5v and 12v outputs to supply the current loop channel. (Some instruments require 5v / some 12v).
Must also have a 12v output to supply the satellite modem.
Must be able to send RS232 commands to send both input channels to a satellite modem device.
Must have a facility to pull down an input on the satellite modem to make the modem enter a quiescent state on completion of data send.
Must be enclosed with an IP rated enclosure complete with a suitable 12v battery of sufficient capacity and 2no cable glands (1no for the instrument and 1no for the satellite modem).
Additional information added:
The unit must have an on / off switch.
It should be possible to select the frequency of data upload to the satellite modem (20 min / 1hr / 2 hr / 4hr / 24 hr) with the use of internal dip switches.
For reference, the satellite modem is limited to sending 340 bytes of data per message.
I would also like to explore if it would be possible to include flash memory - so that I can update over USB or similar to allow me to update the RS232 commands should this be necessary and so I can upload the scaling for the input channels.
I am using the RockBlock Plus satellite modem and have attached a brochure and developers guide for the satellite modem for those that have asked.
Two channels - 1no 4-20mA current loop and 1no 3k NTC thermistor.
Must be battery powered (12v) and be able to enter a quiescent state to conserve battery power.
Must have regulated 5v and 12v outputs to supply the current loop channel. (Some instruments require 5v / some 12v).
Must also have a 12v output to supply the satellite modem.
Must be able to send RS232 commands to send both input channels to a satellite modem device.
Must have a facility to pull down an input on the satellite modem to make the modem enter a quiescent state on completion of data send.
Must be enclosed with an IP rated enclosure complete with a suitable 12v battery of sufficient capacity and 2no cable glands (1no for the instrument and 1no for the satellite modem).
Additional information added:
The unit must have an on / off switch.
It should be possible to select the frequency of data upload to the satellite modem (20 min / 1hr / 2 hr / 4hr / 24 hr) with the use of internal dip switches.
For reference, the satellite modem is limited to sending 340 bytes of data per message.
I would also like to explore if it would be possible to include flash memory - so that I can update over USB or similar to allow me to update the RS232 commands should this be necessary and so I can upload the scaling for the input channels.
I am using the RockBlock Plus satellite modem and have attached a brochure and developers guide for the satellite modem for those that have asked.
Sean B.
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Last project
16 May 2017
United Kingdom
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