4-20 mA
Analog signal
Current is proportional and scalable to sensor signal
Carries one measured variable in one direction
Historical standard for measurement & control
|
 |
The standard analog communication protocol for over 20 years. The primary variable is transmitted via a 4-20 mA current loop from the field device to the control system. Only one variable can be transmitted per loop. No secondary data is available for the control system, and the field devices can only be calibrated and configured at the device itself in the fermentation or cell culture suite. |
|
|
4-20 mA current signal |
|
|
HART®
Digital signal superimposed over standard analog 4-20 mA signal
4-20 mA signal carries primary variable, digital signal carries other measurement and configuration data
Bi-directional digital communication enables remote process monitoring and field configuration
Process data can be recorded and trended in a 21 CFR Part 11 compliant format with an interface software package
|
|
A natural evolution of the 4-20 mA protocol, HART is a digital protocol that is superimposed over a conventional 4-20 mA signal, which still carries the primary variable. This digital signal allows the simultaneous transmission of additional measurements to the control system that will enable advanced sensor monitoring and diagnostics. The digital signal is bi-directional which allows the remote monitoring and configuration of the field device by the use of Asset Management Solutions (AMS) software on any networked PC and thus enables remote troubleshooting and reduces false alarms which waste valuable time.
|
|
Digital signal superimposed via frequency shift keying (FSK)
|
|
Foundation™ fieldbus
Purely digital bi-directional communication network connecting field devices and control system
Field devices transmit multiple variables which enable advanced control and diagnostics
Plug-and-Play enabled field devices connect to control network and allow ease of configuration
Field devices utilize a single standard cable for data transfer and to provide power |
|
Foundation fieldbus is a fully digital, bi-directional, communications protocol used for communications between field devices and control systems. The protocol allows for these devices to be drop connected along one field network and loop powered. Additionally they transmit multiple measurement variables to the control system and to other devices for true distributed control. Remote PC workstations can view data trends, perform diagnostics, view alarms, and reconfigure the field device without having to enter the fermentation or cell culture suite. |
|
Foundation H1 digital network
|
|
