Pressure Systems 9046 user manual Summary Information About All Commands

Pressure Systems, Inc. Model 9046 User’s Manual

5.1 Summary Information About All Commands

The command descriptions that follow are listed in the same order as the Quick Reference table above. All TCP/IP commands are listed first (in alphabetical order: first by upper-case letters, then by lower-case letters). A unique TCP "connection" must be established between the host computer and the Model 9046 module before such commands can be sent to the module. Finally, there are a few special UDP/IP commands listed that can be sent to a Model 9046 module without a valid TCP "connection" having to be established. These commands can be sent even if the module currently has no TCP address assigned to it.

The 9046 module can actually make two (2) separate measurements for each of its 16 channels. The first is called the Primary Transducer datum. For modules configured as Thermocouple (TC), RTD, or Thermistor Sensor Types this datum will be the temperature measurement from a particular channel’s active external junction or transducer. This datum is available in engineering units (E. U.) of Centigrade or Fahrenheit degrees (ºC or ºF), raw A/D counts (-32768 to +32767), or volts (-5 to +5). For Resistance Sensor Types this E. U. datum is in ohms instead of degrees, and is available in raw counts or volts, too. The second data measurement available from each channel is called the Other Transducer datum. For Thermocouple (TC) Sensor Types, this datum measures the Uniform Temperature Reference (UTR) junction just inside the module. Its E. U. temperature value is also in ºC or ºF. For all other Sensor Types this other datum measures the Source Voltage: an intermediate measurement used in calculating the Primary Transducer value. Its E. U. value is always expressed in volts. This other datum is also available in raw A/D counts and volts.

Whether any E. U. Temperature datum value (primary or other) is returned in ºC or ºF, in a command response or stream, is a configuration option of any Model 9046 module (see the ’v0110b’ command below). However, temperature values in some setup commands and responses require a fixed ºC value (e.g., the UTR Avg. Deviation Set Point which are written and read (respectively) with the ’w1901’ and ’q0e’ commands below)

The various parameters of most commands (following the single ASCII character operation code) are concise and efficient (but somewhat arcane). Such parameters are mostly variable- length hexadecimal digit fields. Most hexadecimal fields (1 or more hex digits in width) represent the values of simple positive integers, which may represent format choices, modes, or other similar numerical quantities. However, some represent bit maps; which are usually four hex digits (representing 16 discrete internal bits, numbered 16-1, left-to-right). Usually each bit represents some on/off (1/0) state, which could be the contribution of a particular channel number (e.g., 16-1), or the presence of a particular type of data grouping in a stream. Other decimal or hexadecimal digit fields may optionally appear following the first space character in some commands. Please note that all command operation codes are case-sensitive letters (i.e., command ’A’ and command ’a’ are different commands). However, all "alpha numbers" (a-f or A-F) that are valid of hexadecimal digits are not case sensitive (i.e., 12e4f and 12E4F and 12e4F are the same hex number).

Command responses returned by the Model 9046 module often contain only a simple A (Ack) or N (Nak) character, indicating the success or failure of the command sent to it. These responses may be followed, or replaced, by one or more hexadecimal or decimal values, as indicated in the particular command description below. If the response is "pure data", requested by some

Page 30 www.PressureSystems.com