MODEL AT-10

ANALOG TRANSMITTER

INSTALLATION & OPERATING

MANUAL

Precise Instrument Corp.

76 Winn Street
Woburn, MA 01801
Phone: 781-937-3115 Fax: 781-937-3116
www.preciseinstrument.com

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 SECTION I FIGURE 4
GENERAL INFORMATION Model 121 Power Supply

Introduction

The Model AT-10 Analog Transmitters are electronic devices

utilizing solid-state integrated components. They provide the
user with a selectable voltage or current output directly
proportional to the input signal within a specified linearity.
Fuse
Description

The transmitters are intended for field mounting close to the

vessel site, thereby reducing installation costs. An integral
20-position terminal strip provides connections for up to four
transducers, thus eliminating the need for a separate summing
junction box.
L N LED + + - -
Two screw type terminal strips provide connections for the
supply voltage, transducer wiring, and analog outputs. 115 Vac 24 Vdc

The zero and span adjustments for the analog outputs are Fuse Replacement
accomplished with two sets of dip-switches and trim pots.

The units also include an adjustable filter which can be used to

• The following procedures require work inside the power
stabilize the output. Filtering is used to minimize the effects of supply enclosure and should be performed by qualified
vibration caused by agitators or other devices. service personnel.
• Before opening the unit, disconnect the AC voltage.
Each unit is set to customer specifications or factory standards • Remove the front cover from the power supply.
prior to shipment in order to provide a fully tested and working • Press down gently on the cover of the fuse holder, and
instrument. Should a change be required, or to verify the initial turn counter-clockwise.
settings, please follow the procedures outlined in Section II of
the manual. • Pull out the cover and fuse as an assembly, replace fuse
with a new one.
The standard packaging is an ABS plastic DIN-Rail mounted • Re-install fuse and cover as an assembly, press down
enclosure. Optional field-mounted, fiberglass or type 304 gently and turn clockwise.
stainless steel NEMA-4X enclosures are available. • Replace the front cover on the power supply.

The transmitters are available with an optional 24 Vdc power

• Re-apply AC voltage to the unit.
supply enabling the unit to be operated with 115 Vac. For
In the event of a malfunction, please contact the nearest
additional information, please refer to Section III of the manual.
distributor for assistance. Any attempt to modify or repair the
power supply will void the manufacturers warranty.

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 SECTION III Specifications
OPTIONS
Power
Precise Model 121
24 Volt Power Supply Power Supply 24 Vdc + 15%
Load Cell Excitation 10 Vdc
Specifications Load Current 200 mA (4 load cells x 350Ω)
Power Consumption 6 VA
Power
Amplifier
Input Voltage 115 Vac, 50/60Hz
Output Voltage 24 Vdc (norminal) Input Signal Selectable, 10mV, 20mV, 30mV
Power Consumption 10 VA maximum Output Signals Selectable (Internal jumper J1)
Fuse 200 mA Voltage 0-10 Vdc (2KΩ min load)
Isolation Class II Current 4/20 mA (500Ω load max)
Maximum Gain ≈ 4000
Environmental Coarse Zero 4-position dip-switch
Fine Zero 20-turn trim-pot
Operating Temp. Range +14 to +104ºF (-10 to +40°C) Coarse Span Control 4-position-dip switch
Storage Temp. Range -4 to +122ºF (-20 to +50°C) Fine Span Control 20-turn trim-pot
Relative Humidity 85% non-condensing Linearity + 0.02% FS
Analog Filter Adjustable, 270° turn trim-pot
Enclosure
Environmental
Dimensions (L x H x D) 2.75" x 3.50" x 2.25"
Mounting DIN-Rail mount Operating Temp. Range +14 to +104ºF (-10 to +40°C)
Material ABS Plastic Storage Temp. Range -4 to +122ºF (-20 to +50°C)
Weight 12.5 Ounces Thermal Stability 20 ppm/°C
Relative Humidity 85% non-condensing
Installation
Enclosure
• Make sure the installation complies with local regulations Dimensions (L x H x D) 5.0" x 3.5" x 2.5"
and electrical codes. Mounting DIN-Rail mount
• Connect AC voltage to the terminals marked “L” and “N”. Material ABS Plastic
• The DC voltage is available on the terminals marked “+” Weight 7.5 Ounces
and “-”. The second set of terminals are used when Wiring connections Terminal blocks, pitch 0.196
powering two transmitters from a single power supply.
• A red LED is illuminated when the power supply is “ON”. Options

Refer to Figure 4 on the following page for terminal locations. 115 Vac power supply DIN-Rail mounted, (See pg. 10)
NEMA 4X Enclosure Wall mounted, 10” x 8” x 4”

NOTE: All specifications are subject to change.

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 TABLE 2
Span Adjustment Dip-switches

Mount the transmitter horizontally on a section of DIN-Rail with Terminal Block TB1 positioned on the bottom. If an
1 2 3 4 mV mV

optional 115 Vac to 24 Vdc power supply is used, the cable between the two devices must not exceed 3 feet.
min max
OFF OFF OFF OFF 2.6 2.8
ON OFF OFF OFF 2.8 3.0
OFF ON OFF OFF 3.0 3.2
ON ON OFF OFF 3.2 3.5

10 11 12 13 14 15 16 17 18 19 20
OFF OFF ON OFF 3.4 3.7
ON OFF ON OFF 3.7 4.0
OFF ON ON OFF 4.0 4.4
ON ON ON OFF 4.3 4.9
OFF OFF OFF ON 4.8 5.4
ON OFF OFF ON 5.3 6.1
OFF ON OFF ON 5.9 7.0
Wiring Connections

ON ON OFF ON 6.8 8.2

FIGURE 1

OFF OFF ON ON 7.8 9.7

ON OFF ON ON 9.3 12.2
OFF ON ON ON 11.6 16.5
9

ON ON ON ON 15.2 24.7
8

FIGURE 3
7

Analog Filter Adjustment

26 25 24 23 22 21

6
5
4
TB2

TB1

Filter
Adjustment
2
1

TB2
J2 removed = No Filtering J2
J2 installed = Filter Activated

TB1

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 1

ON
ON
ON
ON
ON
ON
ON
ON

OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
2

ON
ON
ON
ON
ON
ON
ON
ON

OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
Analog Filter Adjustment

ON
ON
ON
ON
ON
ON
ON
ON

OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
Calibration Procedure (cont’d)

8
TABLE 1

ON
ON
ON
ON
ON
ON
ON
ON
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
Zero Adjustment Dip-switches

9.3
8.3
7.2
5.9
4.6
3.0
1.2
mV

-0.8
min

14.8
14.3
13.7
13.1
12.5
11.8
11.0
10.2
slowly turn the filter adjustment clockwise until the output
If the output is unstable under normal operating conditions,

9.7
8.4
7.1
5.5
3.7
1.6
mV
stabilizes. See Figure 3 for location of the filter adjustment.

17.3
16.8
16.2
15.7
15.0
14.3
13.6
12.8
11.8
10.8
max
correct output. Turning the trim pot clockwise increases the
Apply a known weight and adjust the fine span trim pot for the

Replace the metal cover after calibration has been completed.

output while turning it counter clockwise decreases the output.

Re-check “zero” and “span” calibration and re-adjust if required.

The Model AT-10 is designed to be installed in the field close to the vessel. Terminal strip TB1 provides connections
for up to four transducers, thereby eliminating the need for a separate summing junction box.

TB1 TB2
1. - Excitation (cell # 1) 11. - Excitation (cell # 3) 21. + 4/20 mA
2. + Excitation (cell # 1) 12. + Excitation (cell # 3) 22. + 0-5 / 0-10 Vdc
3. - Signal (cell # 1) 13. - Signal (cell # 3) 23. - Analog Output
4. + Signal (cell # 1) 14. + Signal (cell # 3) 24. - 24 Vdc (supply)
5. Shield 15. Shield 25. + 24 Vdc (supply)
5

6. - Excitation (cell # 2) 16. - Excitation (cell # 4) 26. Ground

7. + Excitation (cell # 2) 17. + Excitation (cell # 4)
8. - Signal (cell # 2) 18. - Signal (cell # 4)
9. + Signal (cell # 2) 19. + Signal (cell # 4)
10. Shield 20. Shield

NOTE: Some transducer manufacturers utilize a 6-conductor cable (+/- Sense leads). When using these type of
transducers, the + Sense lead must be connected to the + Excitation terminal and the - Sense lead must be
connected to the - Excitation terminal.
 SECTION II
CALIBRATION

Prior to calibrating the instrument perform the following Calibration Procedure

calculations. This will enable you to determine where the
dip-switches should be positioned for zero and span. Obtain Remove the metal cover to expose the dip-switches, jumpers
the capacity and full scale output of the transducer/s from the and trim pots as shown in Figure 2 below.
calibration certificates. If required, convert them into the
engineering units being used in the system. Set the zero and span dip-switches so the calculated values are
within the minimum and maximum mV ranges given in Tables 1
Use the above values in the following formulas to determine the and 2.
zero and span mV values.
Position jumper J1 for current or voltage output. See Figure 2.
Multiply the full scale mV/V output of the transducer/s by the
excitation voltage to obtain mV. Connect a digital multi-meter to terminal strip TB2 terminals 21
and 23 for current output or to terminals 22 and 23 for voltage
Example: 3.0 mV/V x 10 Vdc = 30 mV. output.

Zero (mV) = Z x O / C Apply power to the unit and allow a couple of minutes for the
transmitter to warm up before making any adjustments.
Z = Tare weight (vessel, agitator, etc)
O = Full scale output in mV Remove any weight from the system and adjust the fine zero
C = Total capacity of the transducers. trim pot for a reading 0 Vdc or 4 mA. Turn the trim pot
clockwise to increase the output, or counter-clockwise to
Set the zero adjustment dip-switches so the calculated value is decrease the output.
within the minimum and maximum mV ranges given in Table 1.

Span (mV) = S x O / C
FIGURE 2
S = Net weight (live or product weight) Zero & Span Adjustments
O = Full scale output in mV
C = Total capacity of the transducers.
J1 installed = 4/20 mA
Set the span dip-switches so the calculated value is within the J1 removed = 0-10 Vdc
J1

minimum and maximum mV ranges given in Table 2.

Sample calculation: TB2

ZERO ADJ. SPAN ADJ.

Three 1000 lb. load cells, output = 3.0 mV/V 1 1

2 2
Tare weight = 500 Lbs. 3 3
4 4
Net weight = 2000 Lbs. TB1
3.0 mV/V x 10 Vdc = 30 mV
Zero (mV) 500 Lbs. x 30 mV / 3,000 Lbs. = 5 mV
Table 1 dip-switch setting = Off, On, Off, Off (3.0 to 5.5 mV)
Span (mV) 2000 Lbs. x 30 mV / 3,000 Lbs. = 20 mV
Table 2 dip-switch setting = On, On, On, On (15.2 to 24.7 mV)

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