Preciseline Pressure Transducer (by Keller-America).

In the case of the Preciseline, the water pressure signal is converted into Modbus; whereas in the case of our EtherMeter, error-free totalization and flow-rate data is collected from a compatible flow meter(s) and converted into Modbus .

As I/O counts grow and instrumentation complexity increases in water plants and pump stations, the addition of smart Modbus sensors is a natural solution that can simplify control system integration challenges.

For example, using a multi-drop Modbus/RTU network, a single shielded cable (+24VDC/Gnd, RS485A/RS485B) can be routed throughout a water plant or pump station to communicate with (and provide power to) an assortment of Modbus-based devices.

As an example, Jersey County Rural Water Company (Jerseyville, IL) recently completed construction of a new pumping station at Godfrey, IL.  The control system at the station features a Modbus/RTU multi-drop network that communicates to 3 Preciseline transducers which monitor station effluent pressure, influent pressure, and the level of water in the ground storage tank.

The same network also includes 2 EtherMeters, which report totalization and flow-rate from 4 flow meters (2 Sensus Omni-T2 meters and 2 Neptune HP Turbine meters).

3 Preciseline pressure transducers and 1 EtherMeter connected to the pump station’s multi-drop Modbus/RTU (RS485) network. The transducers are monitoring effluent pressure, influent pressure, and ground storage tank level. (Click to zoom.)

Had this project been addressed using legacy analog methods, then the aforementioned signals would have required 7 shielded cables connected to an RTU via 3 analog-digital converters and 4 pulse-counting channels.

Therefore, the use of Modbus may significantly reduce the costs associated with wiring, conduit, and instrumentation.  Furthermore, the future addition of other Modbus-based devices is highly simplified.

An EtherMeter-connected, 6″ Sensus Omni-T2 meter. One of four meters in the pump station. (Click to zoom.)

In this application, Jersey County’s potential upgrade plans include tying the 3 variable-speed drives, 3 motorized valves, backup generator, power meter, and Chlorine Monitor into the Modbus network.

Modbus/RTU network schematic. (Click to zoom.)

On 03 Sep 2010, Jersey County Rural Water Co. is hosting a Dedication Ceremony and Open House for the Pump Station featured in this article. The described Modbus flow metering and pressure monitoring technology will be displayed at this event. If interested in attending, please contact Jim Mimlitz at SCADAmetrics (636)938-9633.

For further information on the Preciseline and other Modbus-capable pressure transducers, please contact Chris Lilly at Keller-America (757)596-6680.

[original article located at: http://scadametrics.com/blog/?p=205]

1) A Trimble Nomad (or similar Windows Mobile¹).

2) RS232 port boot option (USB interfaces are not supported for the Logger CE software).

3) Keller DCX series data-logger

4) Keller K-103A RS232-to-RS485 converter

Notes:

¹ While Keller data-loggers and interface converters will theoretically work with any Windows Mobile device that supports a physical RS232 communications port, due to the myriad of hardware implementations we can only provide support for the Trimble Nomad device at this time.

Step 1 – Installing the Logger CE software

Download the Keller Logger CE software from this link: http://www.kelleramerica.com/manuals-and-software/software/CE_Logger.exe

At this point make sure that your Windows Mobile device is connected to your PC and configured to work with Microsoft ActiveSync (consult your Windows Mobile device documentation for details).

To install the Logger CE software simply run the executable file you downloaded previously. Once installed, the Windows Mobile device should prompt you to reboot. After that, the software should be installed and available to use in your Programs folder.

Step 2 – Connecting the interface converter and data-logger

This is fairly straight forward; just plug in the K-103A interface in to the RS-232 port of the Windows Mobile device. Then connect your DCX series data-logger to the the K-103A (please note that an optional cable is required for use with the DCX Eco line of data-loggers).

Step 3 – Running the Reader CE & Writer CE software

A full explanation of all the features of these two applications is beyond the scope of this article, however I will give you a brief overview. You can consult our Logger DCX software manual for more details on the various features and options within the Reader CE & Writer CE software.

Writter CE – This application allows you configure the various setup options for your data-logger. For example, you can configure the logger to log data at regular intervals, or to only log once an event trigger occurs.

Reader CE – This application will allow you to read out the data collected by the data-logger. This data can be views on the mobile device, or with our desktop Logger DCX software suite for more robust viewing options. If your mobile device supports WiFi you can also email these data files to another location.

This guide will help walk you through the configuration required to use a Keller MODBUS-capable level or pressure transmitter with the Precision Digital PD865 display. Jose, from Precision Digital, recently made video using this very same configuration, which you can watch here.

So just what is the PD865? The PD865 (also called ‘Snooper MODBUS Meter’) is an advanced panel meter made by Precision Digital that can poll and display data from the registers of virtually any device that supports MODBUS Function 3 or 4. It just so happens that Keller digital pressure & level transmitters fully support MODBUS Function 3. This means that we can use the PD865 (or virtually any other MODBUS capable panel meter) to display pressure or temperature data as measured by the Keller transmitter.

To accomplish this you will need at least one Keller digital transmitter, such as the Acculevel or Preciseline, and at least one Precision Digital PD865 (two if you wish to display pressure and temperature simultaneously). That’s it!

Here are some files that you may find helpful if you wish to do more than what is outlined in this basic guide:

PD865 Manual

Keller Transmitter User Guide

Series 30 Protocol Documentation (See page 20 for information on MODBUS as it relates to Keller transmitters)

Application note for using a PD865 & Keller transmitters

Connecting the devices:

Connect the Keller transmitter to the PD865 according to the following diagram:

Consult page 16 of the PD865 manual for more details.

Configuring the PD865:

Configure the PD865 settings with the following parameters:

Mode = Master

Function = 03

PV Number = 1 (number of PVs)

Slave ID = 001 (Device’s MODBUS address)

Reg. Number PV1 = 40003 (Register 0×02)

Data Type = Float

Byte Order = 1234

Poll Time = 1.0 seconds

Response Timeout = 5.0 seconds

Baud = 9600

Parity = none

Stop Bits = 1

Byte-to-Byte Timeout = 0.01 seconds

Configure the scaling of the PD865 with the following settings:

Input 1 = -19.9999

Input 2 = 99.9999

Display 1 = -19999.9

Display 2 = 99999.9

That’s it! Now you should see the pressure displayed on the PD865!

You can also view the video at full resolution on their website: http://www.predig.com/videos/watch.php?Video=16

The data sheet can be downloaded here: http://www.kelleramerica.com/pdf-library/pdf/Microlevel.pdf

Contact Keller America today for more information.

Keller America, Inc. is committed to doing our part to aid the economic recovery by growing our business, building innovative products, and thereby creating jobs for deserving Americans.

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