METER TEROS 21, Integrator Manual

7

COMMAND IMPLEMENTATION

The following tables list the relevant Measurement (

M

), Continuous (

R

), and Concurrent (

C

) commands and 

subsequent Data (

D

) commands when necessary.

MEASUREMENT COMMANDS IMPLEMENTATION

Measurement (

M

) commands are sent to a single sensor on the SDI-12 bus and require that subsequent Data 

(

D

) commands are sent to that sensor to retrieve the sensor output data before initiating communication with 

another sensor on the bus.

Please refer to 

Table 2

 and for an explanation of the command sequence and see 

Table 7 

for an explanation of 

response parameters.

Table 2  

aM!

 command sequence

Command

Response

This command reports average values when relevant.

aM!

atttn

aD0!

a-<waterPotential>±<temperature>

NOTE:  The measurement and corresponding data commands are intended to be used back to back. After a measurement command is 
processed by the sensor, a service request a 

<CR><LF>

 is sent from the sensor signaling the measurement is ready. Either wait until 

ttt

seconds have passed or wait until the service request is received before sending the data commands. See the 

SDI-12 Specifications v1.3

document for more information.

CONCURRENT MEASUREMENT COMMANDS IMPLEMENTATION

Concurrent (

C

) measurement commands are typically used with sensors connected to a bus. Concurrent (

C

) 

commands for this sensor deviate from the standard 

C

 command implementation. First, send the 

C

 command, 

wait the specified amount of time detailed in the 

C

 command response, and then use 

D

 commands to read its 

response prior to communicating with another sensor.

Please refer to 

Table 3

 for an explanation of the command sequence and see 

Table 7 

for an explanation of 

response parameters. 

Table 3  

aC!

 measurement command sequence

Command

Response

This command reports average values when relevant.

aC!

attnn

aD0!

a-<waterPotential>±<temperature>

NOTES: This command does not adhere to the SDI-12 concurrent command requirements. See 

METER SDI-12 Implementation

 for more 

information.
The measurement and corresponding data commands are intended to be used back to back. After a measurement command is processed 
by the sensor, a service request a 

<CR><LF>

 is sent from the sensor signaling the measurement is ready. Either wait until 

ttt

 seconds have 

passed or wait until the service request is received before sending the data commands. See the 

SDI-12 Specifications v1.3

 document for 

more information.

CONTINUOUS MEASUREMENT COMMANDS IMPLEMENTATION

Continuous (

R

) measurement commands trigger a sensor measurement and return the data automatically 

after the readings are completed without needing to send a 

D

 command.  

Please refer to 

Table 4

 through 

Table 6

 for an explanation of the command sequence and see 

Table 7

 for an 

explanation of response parameters. 

Table 4  

aR0!

 measurement command sequence

Command

Response

This command reports instantaneous values. 

aR0!

a-<waterPotential>±<temperature>

NOTE:  This command does not adhere to the SDI-12 response timing. See 

METER SDI-12 Implementation

 for more information.