in reply to: calibrating a hart device posted by payal on 06 February 2006 at 05:25:06.
I'm not sure exactly what you propose, Payal.
You can configure the output range for a device in multidrop, at any time, by specifying its polling address (1 to 15 in HART revision 5).
And you can do the PV trim part of the calibration in multidrop, by feeding the transmitter from a standard calibrated source (a resistance box for a PRT, or a calibrated pressure source, or whatever suits the transmitter) at the lower range value, and using a HART master (such as handheld configurator) to send command #43 ("set PV zero").
But to trim the analogue output, you will have to set the polling address to 0 (I am assuming HART revision 4 or 5 devices - rev. 6 is different), and disconnect all other devices, so that you can measure the current. Then you can use command #40 ("enter/exit fixed current mode") from your HART master to force one of the end-of range values (4.0mA, 20.0mA) and command #45 ("trim DAC zero") and #46 ("trim DAC gain") to make the adjustments. You need an accurate digital current meter to do this.
There are two very helpful articles on calibration of HART devices at http://www.thehartbook.com/articles/h8calibrating.asp and http://www.thehartbook.com/articles/h10maintenance.asp.