Introduction

The Corrosive Liquid Sampler CLS 700T is a computer controlled particle counter which is designed to work in conjunction with Particle Measuring Systems' LiQuilaz particle counter. Commands are issued to the CLS 700T and internal LiQuilaz either through the RS-232 or RS-485 port on the back panel. The CLS 700 supports what is referred to as Slow Protocol. The LiQuilaz particle counter supports Slow Protocol but can also utilize a Fast Protocol which is described separately in the LiQuilaz manual.

This technical note was written for the express purpose to outline the communication requirements as applied to a CLS-700 / LiQuilaz instrument combination. Both devices must be communicated separately via different network addresses. The CLS-700 employs hardware lines to control when the LiQuilaz particle counter is actively sampling. Only the CLS-700T command/response sequence pairs are described in detail. Refer to the LiQuilaz manual for a complete description of the LiQuilaz communication requirements.

Slow Protocol Command Packeting and Formatting

The general communication procedure defined by the Slow Protocol requires what is called a command/response sequence pair. For each command directed to a CLS 700, an appropriate response is generated by the CLS 700. The content of the response is dependent on the particular command (refer to the Slow Protocol Command Summary List for a complete set of CLS 700 commands). Both the commands and responses are formatted and packeted to ensure error free communication. The formatting and packeting process is discussed in the following paragraphs.

Formatting and Packeting Process

The process of building a packet can be divided into the three following steps

Step 1: The address of the device is added to the beginning of the command/response data, and a checksum is added to the end of the command/response data. This produces the following unformatted data structure:

ADDRESS HIGH BYTE | ADDRESS LOW BYTE | FIRST DATA BYTE | SECOND DATA BYTE | ... | LAST DATA BYTE | CHECKSUM HIGH BYTE | CHECKSUM LOW BYTE

Note 1: The use of "|" is for readability and does not appear in the actual data packet.

Note 2: The CHECKSUM entry is a 16 bit unsigned integer sum of the unformatted data including the address with the carry bit ignored if an overflow occurs during the calculation.

Step 2: Minimizes difficulties when the network includes devices such as modems. Only visible ASCII characters (32 126), with the exception of the packet delimiting STX and ETX characters, are transmitted on the network. Non visible and non ASCII characters are run through the conversion formula shown below before they are transmitted.

Step 3: Preface the ASCII packet formed in step 2 with an STX (STX = 2) character and terminate the ASCII packet with an ETX (ETX = 3) character.

Note 3: The STX and ETX characters are used as packet delimiters and are not visible characters but do not cause problems as the NUL, DEL and other 8 bit data characters can. The STX and ETX characters are not included in the checksum.

Slow Protocol Command Description for the CLS 700T

Command Response Function

CFLUSH n RFLUSH n Flush Mode

Where: n = 0 Off, n = 1 On

This command will put the CLS-700 into a Flush Mode. This mode will only be accepted if the CLS-700 is currently in an Idle state. This mode sets a valve configuration such that clean water can be applied to the sample inlet and flushed through the system and exited via the system outlet.

CPURDR n RPURDR n Purge Drain Mode

Where: n = 0 Off, n = 1 On

This command will put the CLS-700 into a Purge Drain Mode. This mode will only be accepted if the CLS-700 is currently in an Idle state. This mode applies internal pressure and sets a valve configuration such that the drain path is purged of residual fluid. Care must be used when requesting this mode of operation as pressurized fluid and gas are purged via the sampler outlet.

CPURIN n RPURIN n Purge Inlet Mode

Where: n = 0 Off, n = 1 On

This command will put the CLS-700 into a Purge Inlet Mode. This mode will only be accepted if the CLS-700 is currently in an Idle state. This mode applies internal pressure and sets a valve configuration such that the inlet path is purged of residual fluid. Care must be used when requesting this mode of operation as pressurized fluid and gas are purged via the sampler inlet.

CPURSEN n RPURSEN n Purge Sensor Mode

Where: n = 0 Off, n = 1 On

This command will put the CLS-700 into a Purge Sensor Mode. This mode will only be accepted if the CLS-700 is currently in an Idle state. This mode applies internal pressure and sets a valve configuration such that the sample path is purged of residual fluid. Care must be used when requesting this mode of operation as pressurized fluid and gas are purged via the sampler outlet.

CRF RRF Clear Error Flags

This command will clear any error bits presented in the Error Mask portion of the RSTATUS response of the CLS-700. All errors are persistent and require the use of the CRF command to be cleared.

CSCT n RSCT n Set Compress Time

Where: n = Integer Time in seconds

This command will set a compression time in seconds. Compression can be used to help force bubbles back into solution prior to forcing the liquid through the particle counter. Compression is applied after Vacuum but prior to the Tare and Sample states.

CSDRAIN n RSDRAIN n Set Drain Timeout

Where: n = Integer Time in seconds

This command will set a drain timeout in seconds. Drain timeout is used to qualify a maximum amount of time that can pass before the CLS-700 sets an error in the Error Mask portion of the RSTATUS response. A drain timeout signifies an error in the fluid handling process or on-board fluid detection system.

CSET n RSET n Set Valve Configuration

Where: n = 0 refused, n = 1 accepted

This command will set a manually setup hardware configuration internal to the CLS-700. This mode will only be accepted if the CLS-700 is currently in a Manual state. Care must be used when setting internal hardware configurations as fluid and gas can be purged via the sampler inlet, outlet, and vent ports.

CSFILL n RSFILL n Set Fill Timeout

Where: n = Integer Time in seconds

This command will set a fill timeout in seconds. Fill timeout is used to qualify a maximum amount of time that can pass before the CLS-700 sets an error in the Error Mask portion of the RSTATUS response. A fill timeout signifies an error in the fluid handling process or on-board fluid detection system.

CSMAN RSMAN n Manual Mode

Where: n = 0 refused, n = 1 accepted

This command will put the CLS-700 into a Manual Control Mode. This mode will only be accepted if the CLS-700 is currently in an Idle state. This mode will allow subsequent CSET commands to be issued which will manually setup a hardware configuration internal to the CLS-700. Care must be used when setting internal hardware configurations as fluid and gas can be purged via the sampler inlet, outlet, and vent ports.

CSPT n RSPT Set Purge Time

Where: n = Integer Time in 20msec increments

CSR RSR Software Reset

This command will force the CLS-700 to perform a full software reset. After a reset or a power-up sequence the CLS-700 will apply a safe hardware configuration.

CSS RSS n Start Sample

Where: n = 0 refused, n = 1 accepted

This command will start the CLS-700 to perform a single sample sequence.

CSSENSOR n RSSENSOR n Set Sample Timeout

Where: n = Integer Time in seconds

This command will set a sample timeout in seconds. Sample timeout is used to qualify a maximum amount of time that can pass before the CLS-700 sets an error in the Error Mask portion of the RSTATUS response. A sample timeout signifies an error in the fluid handling process or on-board fluid detection system.

CSTARE n RSTARE n Set Tare Time

Where: n = Integer Time in seconds

This command will set a tare time in seconds. Tare can be used to ensure that the small amount of fluid that remained between the CLS-700 and the LiQuilaz particle counter from the last sample is pushed through the sensor prior to counting particles. Tare is applied just prior to the Sample state

This command will request the current status of the CLS-700. The CLS-700 status is comprised of a number of fields. The values that each field can take are described at the end of this section. The fields are described as follows:

Valve Mask - Current valve settings

Sensor Mask - Current state of the fluid detectors & pressure switch

State - Current state of the system

Error Mask - Any detected errors

Fill Time - Last measured fill time in seconds

CTS RTS Terminate Sample

This command will stop the CLS-700 regardless of where it is in the sample sequence. Care should be taken when using this command as the CLS-700 could be left with fluid in the Burette, Overflow, Drain, and sensor.

CVAC n RVAC n Set Vacuum Time

Where: n = Integer Time in seconds

This command will set a vacuum time in seconds. Vacuum can be used to help pull excesss bubbles out of solution prior to forcing the liquid through the particle counter. Vacuum is applied before Compression and prior to the Tare and Sample states.

CVER CVER s Get Software Version

Where: s = Software Version String

This command will request the current firmware version of the CLS-700.

XXXXX R?? All other commands

Any unrecognized command will be processed as depicted above.

Typical Sample Flow Rate Processing

The flow rate of the system can be approximated using the following calculation. The approximation will only be good for the next sample processed after the last system adjustment.

The definition of terms is as follows:

Variable Symbol Units Source

Burette Volume BV ml Known (Nominal 48)

Flow Interval FI sec Calculated

Flow Rate FR ml/min Calculated

Sample Interval SI sec Reported

Sample Volume SV ml Calculated

Tare Interval TI sec Known

The calculations are as follows

FI = SI + TI<

FR = (BV / FI) * ( 60sec / 1min)

SV = BV - (FR TI) (1min / 60sec)

Contact us if you need more information or have questions.

Author: Ed Terrell, Particle Measuring Systems

Published: 2003