Seametrics PT12 Manuale utente

Precision Environmental Sensors

An ON

CON Brand

PROUDLY

MADE

IN THE

USA

ISO

9001:2008

PT12

Pressure/Temperature Sensor

Instructions

For PSIG

sensors, refer

to page 16

regarding

desiccant

use!

For Sales & Service Contact

2650 E. 40th Ave. • Denver, CO 80205

Phone 303-320-4764 • Fax 303-322-7242

1-800-833-7958

www.geotechenv.com

PT12 INSTRUCTIONS

Seametrics • 253.872.0284 Page 2 seametrics.com

General Information

General Information ...................................................................................................................................................Page 3

Dimensions ....................................................................................................................................................................Page 3

Specications ................................................................................................................................................................Page 4

How Pressure Sensors Work....................................................................................................................................Page 5

Initial Inspection and Handling..............................................................................................................................Page 6

Do’s and Don’ts............................................................................................................................................................Page 6

Installation

Cable Wiring..................................................................................................................................................................Page 7

Installing the Sensor...................................................................................................................................................Page 7

Desiccant Use................................................................................................................................................................Page 7

Grounding Issues.........................................................................................................................................................Page 8

Sensor/Data Logger Conguration ......................................................................................................................Page 8

Operation/Modbus RTU

Power Consideration ..................................................................................................................................................Page 9

Communication Settings ..........................................................................................................................................Page 9

Modbus Functions.......................................................................................................................................................Page 9

Register Denitions.....................................................................................................................................................Page 9

Sensor Conguration/Control ................................................................................................................................Page 10

Readings and the Auto-Enable Setting...............................................................................................................Page 10

Calibration and Conversion Constants................................................................................................................Page 10

Operation/SDI-12

Reading via SDI-12......................................................................................................................................................Page 11

Calibration Register Denitions .............................................................................................................................Page 15

Maintenance

Removing Debris from End Cone..........................................................................................................................Page 16

Desiccant Tubes ...........................................................................................................................................................Page 16

Sensor/Cable/End Connections .............................................................................................................................Page 17

Troubleshooting

Problems/Probable Causes/Things to Try..........................................................................................................Page 18

TABLE OF CONTENTS

PT12 INSTRUCTIONS

Seametrics • 253.872.0284 Page 3 inwusa.com

GENERAL INFORMATION

The Seametrics PT12 Pressure/Temperature Sensor

has been designed to provide trouble-free submersible

operation in liquid environments. This sensor communicates

via SDI-12 (v1.3) or Modbus®RTU (RS485)protocol.

Pressure/level is measured with an extremely rugged and

stable piezo-electric, media isolated pressure element

and compensated for temperature using Seametrics’

proprietary calibration methodology. Temperature is

measured using an on-board digital chip.

Seametrics also carries a special version of the PT12

designed to measure barometric pressure in reference

to absolute pressure. If you are using an absolute PT12,

contact your representative for details on how our PT12-BV

can facilitate obtaining barometrically compensated

pressure/level.

Dimensions

8.44” (21.4 cm)

0.28” (0.7 cm) Water inlets

Diameter

0.75” (1.9cm)

PT12 INSTRUCTIONS

Seametrics • 253.872.0284 Page 4 seametrics.com

Specications*

GENERAL INFORMATION

Housing & Cable Weight 0.8 lb. (0.4 kg)

Body Material 316 stainless or titanium

Wire Seal

Material Fluoropolymer and PTFE

Cable Submersible: polyurethane, polyethylene, or ETFE; 4 lb./100 ft., 1.8 kg/30 m; 2000 ft max for Modbus®

Desiccant 1-3 mm indicating silica gel

Field Connector Available as an option

Temperature Operating Range Recommended: -15˚ to 55˚C (5˚ to 131˚F) Requires freeze protection kit if using pressure option in water

below freezing.

Storage Range -40˚ to 80˚C (-40˚ to 176˚F)

Power Voltage 9-16Vdc, 24Vdc over voltage protection, electromagnetic & transient protection IEC-61000 - 4-3, 4-4,

4-5, 4-6

Supply Current Active 3mA average/ 10mA peak; sleep 150 µA

Communication Modbus® RS485 Modbus® RTU, output=32bit IEEE oating point

SDI-12 SDI-12 (ver. 1.3) - ASCII

Output Channels Temperature Depth/Level¹

Element Digital IC on board Silicon strain gauge transducer, 316 stainless or Hastelloy

Accuracy ±0.5°C — 0° to 55°C (32˚ to 131˚F)

±2.0°C — below 0°C (32˚F)

±0.05% FSO (typical, static)

±0.1% FSO (maximum, static)

(B.F.S.L. 20˚C)

Resolution 0.06˚C 0.0034% FS (typical)

Range -15˚ to 55˚C (5˚ to 131˚F) Gauge

Absolute3

PSI: 12, 5, 7, 15, 30, 50, 100, 300

FtH₂O: 2.32, 12, 35, 69, 115, 231, 692

mH₂O: 0.72, 3.5, 5, 10.5, 21, 35, 70, 210

PSI: 30, 50, 100, 300

FtH₂O: 35, 81, 196, 658

mH₂O: 10, 24, 59, 200

Compensated --- 0˚ to 40˚C (32˚ to 104˚F)

Max operating pressure 1.1 x full scale

Over pressure protection 3x full scale up to 300psi - for > 300psi (650 ft or 200 m) contact factory

Burst pressure 1000 psi (approx. 2000 ft or 600 m)

Environmental IP68, NEMA 6P

*Specications subject to change. Please consult out web site for the most current data (seametrics.com). Modbus is a registered trademark of Schneider Electric.

1 Higher pressure ranges available upon request

2 ±0.25% accuracy FSO (max) at this range

3 Depth range for absolute sensors has 14.7 PSI subtracted to give actual depth allowed.

PT12 INSTRUCTIONS

Seametrics • 253.872.0284 Page 5 inwusa.com

GENERAL INFORMATION

How Pressure Sensors Work

Liquids and gasses do not retain a xed shape. Both

have the ability to ow and are often referred to as

uids. One fundamental law for a uid is that the uid

exerts an equal pressure in all directions at a given level.

Further, this pressure increases with an increasing depth of

“submergence”. If the density of a uid remains constant

(noncompressible...a generally good assumption for water

at “normal” pressures and temperatures), this pressure

increases linearly with the depth of “submergence”.

We are all “submerged” in the atmosphere. As we increase

our elevation, the pressure exerted on our bodies decreases

as there is less of this uid above us. It should be noted

that atmospheric pressure at a given level does vary

with changes in the weather. One standard atmosphere

(pressure at sea level at 20º C) is dened to be 14.7 PSI

(pounds per square inch).

There are several methods to reference a pressure

measurement. Absolute pressure is measured with respect

to an ideal vacuum (no pressure). Gauge pressure is the

most common way we express pressure in every day life

and is the pressure exerted over and above atmospheric

pressure. With this in mind, gauge pressure (Pg) can be

expressed as the dierence between the absolute pressure

(Pa) and atmospheric pressure (Patm):

Pg = Pa - Patm.

To measure gauge pressure, atmospheric pressure is

subjected to one side of the system and the pressure to be

measured is subjected to the other. The result is that the

dierential (gauge pressure) is measured. A tire pressure

gauge is a common example of this type of device.

Recall that as the level of submergence increases (in a

noncompressible uid), the pressure increases linearly.

Also, recall that changes in weather cause the absolute

atmospheric pressure to change. In water, the absolute

pressure (Pa) at some level of depth (d) is given as follows:

Pa = Patm + kd

where k is simply a constant

(i.e.: 2.307 feet of water = 1 PSI)

Seametrics’ standard gauge submersible pressure

devices utilize a vent tube in the cable to allow the

device to reference atmospheric pressure. The resulting

gauge pressure measurement reects only the depth of

submergence. That is, the net pressure on the diaphragm

is due entirely to the depth of submergence.

Pressure Diagram: See Detail A.

Absolute pressure is given as Pa = Patm + kd

(where k is 2.307 feet of water)

Water Line

Patm

P = Patm + kd

“A”

PT12 INSTRUCTIONS

Seametrics • 253.872.0284 Page 6 seametrics.com

GENERAL INFORMATION

Initial Inspection and Handling

Upon receipt of your sensor, inspect the shipping package for damage. If any damage is apparent, note the signs of

damage on the appropriate shipping form. After opening the carton, look for concealed damage, such as a cut cable. If

concealed damage is found, immediately le a claim with the carrier.

Check the etched label on the sensor to be sure that the proper range and type were provided. Also check the label

attached to the cable at the connector end for the proper cable length.

Do’s and Don’ts

Don’t drop into well

Lower gently to prevent

damage

Don’t scrape cable

over edge of well

May nick or fray the

cable

Don’t bend cable sharply

May close o vent tube

and/or weaken internal

wires

Don’t support sensor

with the connector

Use a strain relief device

Do handle sensor with

care

Do store sensor in a

dry, inside area when

not in use

 

Do install a desiccant

tube if using a gauge

sensor

Do not disassemble—

will void warranty!

PT12 INSTRUCTIONS

Seametrics • 253.872.0284 Page 7 inwusa.com

INSTALLATION

Cable Wiring

For SDI-12

White

Purple

Yellow

Brown

Blue

Shield

12 VDC+ (Vaux)

Modbus D- (Not used)

Modbus D+ (Not used)

SDI-12 Signal

12 VDC- (GND)

Earth ground

For Modbus®

— with optional 5-pin connector

White

Purple

Yellow

Brown

Blue

Shield

12 VDC+ (Vaux)

Modbus D-

Modbus D+

SDI-12 (Not used)

12 VDC- (GND)

5-Pin

Connector

For Modbus®

White

Purple

Yellow

Brown

Blue

Shield

12 VDC+ (Vaux)

Modbus D-

Modbus D+

SDI-12 Signal (Not used)

12 VDC- (Gnd)

Earth ground

For SDI-12

— with optional 5-pin connector

White

Purple

Yellow

Brown

Blue

Shield

12 VDC+ (Vaux)

Modbus D- (Not used)

Modbus D+ (Not used)

SDI-12 Signal

12 VDC- (GND)

5-Pin

Connector

Installing the Sensor

ThePT12 measures pressure. Themost common application

is measuring liquid levels in wells and tanks. In order to do

this, the sensor must be installed below the water level at a

xed depth. The installation depth depends on the range

of the sensor. One (1) PSI is equal to approximately 2.31

feet of water. If you have a 5 PSI sensor, the range is 11.55

feet of water and the sensor should not be installed at a

depth below 11.55 feet. If the sensor is installed below its

maximum range, damage may result to the sensor and the

output reading will not be correct.

• Lower the sensor to the desired depth.

• Fasten the cable to the well head using a weather

proof strain-relief system. When securing a vented

cable, make sure not to pinch the cable too tightly

or the vent tube inside the cable jacket may be

sealed o.

• Take a measurement to insure the sensor is not

installed below its maximum range.

For vented sensors, install the sensor so that the desiccant

tube will not ood or lie in water.

The sensor can be installed in any position; however, when

it leaves the factory it is tested in the vertical position.

Strapping the sensor body with tie wraps or tape will not

hurt it. Seametrics can provide an optional 1/4” NPT input

adapter which is interchangeable with the standard end

cone for those applications where it is necessary to directly

attach the sensor to a pipe, tank, or other pipe port. If the

sensor is being installed in a uid environment other than

water, be sure to check the compatibility of the uid with

the wetted parts of the sensor.

Desiccant Use

On vented sensors a desiccant tube prevents moisture in

the air from being sucked into the vent tube, which can

cause erratic readings and sensor damage.

The desiccant tube is lled with blue silica gel beads. A

locking barb and a hydrophobic water lter are attached to

the end of the desiccant tube. This lter prolongs the life of

the desiccant as much as three times over a desiccant tube

without the lter.

Install the sensor so that the desiccant tube and cable

connector will not ood or lie in water.

The desiccant is a bright blue color when active and dry. See

Maintenance section for care and changing of desiccant.

PT12 INSTRUCTIONS

Seametrics • 253.872.0284 Page 8 seametrics.com

INSTALLATION

Grounding Issues

It is commonly known that when using electronic

equipment, both personnel and equipment need to be

protected from high power spikes that may be caused by

lightning, power line surges, or faulty equipment. Without

a proper grounding system, a power spike will nd the path

of least resistance to earth ground—whether that path

is through sensitive electronic equipment or the person

operating the equipment. In order to ensure safety and

prevent equipment damage, a grounding system must be

used to provide a low resistance path to ground.

When using several pieces of interconnected equipment,

each of which may have its own ground, problems with

noise, signal interference, and erroneous readings may be

noted. This is caused by a condition known as a Ground

Loop. Because of natural resistance in the earth between

the grounding points, current can ow between the points,

creating an unexpected voltage dierence and resulting

erroneous readings.

The single most important step in minimizing a ground

loop is to tie all equipment (sensors, data loggers,

external power sources, and any other associated

equipment) to a single common grounding point.

Seametrics recommends the following:

• The sensor cable shield (the wrapped shield inside

the cable) be attached to the power ground on the

data logger

• The grounding lug be connected via a 12 AWG

or larger wire, to a grounding rod driven into the

earth.

• If you are using an external power supply to power

the data logger that it be tied to the same earth

ground.

Sensor/Data Logger Conguration

The PT12 submersible pressure/temperature transducer is

designed for use with SDI-12 or Modbus®data loggers.

Every sensor is individually calibrated at the factory, using

an environmental test chamber and dead-weight tester.

Sensor specic calibration values are stored in the sensor.

When taking measurements, the internal microprocessor

uses these calibration values to thermally compensate the

pressure readings.

In addition to the factory set calibration values, the user can

enter a eld calibration slope and oset for the pressure

and temperature channels. Pressure readings default to

psi and temperature readings to degrees Celsius. The user

can enter a units conversion slope and oset to change

units, if desired. See the operation sections for details on

changing these values. The power supply voltage channel

always returns values in volts.

PT12 INSTRUCTIONS

Seametrics • 253.872.0284 Page 9 inwusa.com

OPERATION/MODBUS RTU

This section explains how to read your PT12 via Modbus®

RTU. (If you want to read via SDI-12, see the next section

beginning on page 11.)

Power Consideration

If your sensor is not powered continuously by an auxiliary

power supply, then you must turn power on to the sensor

at least two seconds before a reading is to be taken to

allow the sensor to warm up.

Communication Settings

The PT12 is congured to communicate with 8 data bits,

one stop bit, and no parity. Default baud rate is 19200.

Modbus®Functions

All readings are obtained using Modbus®function 03-Read

Holding Registers. Readings are located in two registers

each. The data is returned as a 32-bit IEEE oating-point

value, high word rst, also referred to as big-endian, oat

inverse, or Float AB CD.

Channel Registers Using High Addressing—to match Seametrics Smart Sensors

(Available with rmware 0.13 and higher)

Zero-Based One-Based +40,001

Pressure 62592 62593 462593

Temperature 62594 62595 462595

Power Supply Voltage 62596 62597 462597

Averaged Pressure 62598 62599 462599

Maximum Pressure 62600 62601 462601

Minimum Pressure 62602 62603 462603

Averaged Temperature 62604 62605 462605

Channel Registers Using Standard Addressing

Zero-Based One-Based +40,001 +400,001

Pressure 0 1 40001 400001

Temperature 2 3 40003 400003

Power Supply Voltage 4 5 40005 400005

Averaged Pressure 6 7 40007 400007

Maximum Pressure 8 9 40009 400009

Minimum Pressure 10 11 40011 400011

Averaged Temperature 12 13 40013 400013

The physical register addresses on the PT12 start numbering

from zero – the rst address is 0, the second is 1, etc. On the

other hand, Modbus® protocol considers the rst logical

address to be 1, the second logical address to be 2, etc. For

example, to take a pressure reading you have to read the

physical address 0.

Some programs and equipment when asked to read

address 0 will read that physical address. Others however

will read that logical address, which is actually the physical

address -1 (which does not exist). With these programs and

equipment you must add a one to the address – thus in this

example you would request a read at address 1.

Still other programs and equipment require the addition

of 40,000 or 400,000 to the address to indicate reading

holding registers. These usually also require the addition of

one to the physical address. Check with your program and/

or equipment documentation to determine what style of

Like many common Modbus®devices the PT12 returns

readings starting at register address 0 (or 1 if using one-

based addressing). In addition, for compatibility with other

Seametrics Smart Sensor equipment, the PT12 also returns

these same readings starting at a register address 62592 (or

62593 if using one-based addressing).

PT12 INSTRUCTIONS

Seametrics • 253.872.0284 Page 10 seametrics.com

OPERATION/MODBUS RTU

Calibration and Conversion Constants

The data is returned as a 32-bit IEEE oating-point value,

high word rst, also referred to as big-endian, oat inverse,

or Float AB CD.

Field calibration values and units conversion values can be

set by the user. If set, these values will be applied to the

readings before values are returned.

Zero-

Based

One-

Based

+40,001 Description

200-01 201-02 40201-02 Factory Calibration* - Pressure Scale

202-03 203-04 40203-04 Factory Calibration* - Pressure Linearization 1

204-05 205-06 40205-06 Factory Calibration* - Pressure Linearization 2

206-07 207-08 40207-08 Factory Calibration* - Pressure Slope 0

208-09 209-10 40209-10 Factory Calibration* - Pressure Slope 1

210-11 211-12 40211-12 Factory Calibration* - Pressure Slope 2

212-13 213-14 40213-14 Factory Calibration* - Pressure Oset 0

214-15 215-16 40215-16 Factory Calibration* - Pressure Oset 1

216-17 217-18 40217-18 Factory Calibration* - Pressure Oset 2

218-19 219-20 40219-20 Field Calibration - Pressure Slope

220-21 221-22 40221-22 Field Calibration - Pressure Oset

222-23 223-24 40223-24 Field Calibration - Temperature Slope

224-25 225-26 40225-26 Field Calibration - Temperature Oset

226-27 227-28 40227-28 Factory Calibration* - Temperature Alpha

228-29 229-30 40229-30 Factory Calibration* - Temperature Oset

230-31 231-32 40231-32 Factory Calibration* - Tempearture Slope

232-33 233-34 40233-34 Pressure Units - Conversion Slope

234-35 235-36 40235-36 Pressure Units - Conversion Oset

236-37 237-38 40237-38 Temperature Units - Conversion Slope

238-39 239-40 40239-40 Temperature Units - Conversion Oset

* Factory calibration values are set at the factory.

Writing to Factory Calibration

registers will void calibration!

Zero-

Based

One-

Based

+40,001 Description

300=n 301=n 40301=n Set averaging: This enables sensor for n

seconds. Each second, the statistical data

registers will be updated to contain new

averages, max and min. At the completion of n

seconds, the nal statistical values will be left in

the registers, and the sensor will be put to sleep.

n = 0..10,800. If n = 0, the sensor is put to sleep,

and the statistical data values are not updated.

400=a 401=a 40401=a Set sensor address = a (Write Only)

500=b 501=b 40501=b Set baud rate = b (Write only)

0=38400, 1=19200 (default), 2=9600, 3=4800,

4=2400, 5=1200

600=w 601=w 40601=w Set auto-enable. Causes sensor to be enabled

automatically for w seconds after a read of any

parameter data register. W=0 disables auto-

enable. (This is normally set to 10 seconds at the

factory.) For lowest power usage, set this to zero.

For fastest readings while still retaining as much

power savings as possible, set slightly longer

than your read frequency. See section below

for information on how this setting aects your

readings.

700=L 701=L 40701=L Set serial number. L= unsigned longword value

0x0000000 .. 0xFFFFFFF (0 .. 4,294,967,295)

800 801 40801 Read sensor rmware revision. Word MSB =

Major revision, LSB = minor revision.

E.g., 0013 = revision 0.13

Sensor Conguration/Control

Readings and the Auto-Enable Setting

When a reading is requested, four things happen:

• The sensor wakes up.

• The current value in the register is returned.

• The sensor turns on the analog portion, begins

sampling, and begins putting the new values in the

registers.

• If auto-enable is set to a positive value w, the sensor

stays awake for w seconds, sampling and moving

values into the registers all the while, and then goes

to sleep.

• If auto-enable is set to zero, the sensor immediately

goes to sleep after putting the reading in the

If your read frequency is less than the auto-enable value,

the sensor will stay on continuously, and your readings will

always be fresh, with the exception of the very rst reading.

If your read frequency is greater than the auto-enable

value, the following reading sequence is recommended:

1. Request a reading. This begins the wakeup process

on the sensor and returns the value currently in the

away.

2. Wait one second, then take another reading. This

reading will have fresh data. Record this reading.

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