T 7575 EN
Type 3812 Pneumatic Transmitter for TemperatureWith fixed sensor or sensor with capillary tube

Application
Temperature transmitter for use in pneumatic control systems with temperatures from –40 to +300 °C
Instruments for measuring temperatures and converting the measured value into a standardized pneumatic signal from
0.2 to 1.0 bar/3 to 15 psi · Suitable for measuring liquids, gases and vapors

Special features• Wide variety of applications as the nitrogen (N2)-filledbulb of the sensor can be used for various media• Measuring span of 50, 100 or 200 °C• The lower range value can be adjusted within wide limits• Sensor made of stainless steel 1.4571 or 1.4404
VersionsType 3812 · Pneumatic transmitter for temperature with bulb
or spiral sensor · Measuring span 50, 100 or 200 °C · Measuring limits –40 to +300 °C · Measuring range –20 to+30 °C, 0 to +50 °C, 0 to +100 °C, +50 to +150 °C, 0 to+200 °C

Fig. 1: Type 3812, with fixed sensor (standard version)

Version with fixed temperature sensor (Fig. 1) or with temperature sensor connected to the measuring system by a capillary tube (Fig. 2)
Options
Air temperature sensor (outside diameter 20 mm) or temperature sensor for installation in T-unions acc. to DIN 11857 (formilk and other food and beverages)
Special versions–Connection pipe with protective metal hose–

G 1/8 supply air connection instead of 1/8 NPT–Special measuring ranges
Fig. 2: Type 3812 · Sensor with capillary tube

SAMSON AKTIENGESELLSCHAFT · Weismüllerstraße 3 · 60314 Frankfurt am Main, Germany
Phone: +49 69 4009-0 · Fax: +49 69 4009-1507 · samson@samsongroup.com · www.samsongroup.com

Edition February 2020

Principle of operation (see Fig. 3)

10

The temperature of the process medium produces a pressure
proportional to the temperature in the gas-filled sensor (1).
This pressure acts on the measuring bellows (1.3) creating aforce which is measured at the balance beam (3) and converted into a pneumatic signal (pA).
The supply air pZ flows through the booster (8), passes on to
the restriction (9) and the nozzle (7) and finally hits the flapper (6). An increase in temperature causes the flapper tocome closer to the nozzle. As a result, the output pressure pA
supplied to the bellows (5) rises until an equilibrium isreached again, i.e. until the output signal reaches a value
proportional to the temperature.

Temperature measuring 5 Feedback bellows
system6 Flapper plate
1.1 Sensor
7 Nozzle
1.2 Capillary tube
8 Booster
1.3 Measuring bellows
9 Restrictor
2 Base plate
10 Damping
3 Balance beam
11 Zero adjustment
4 Cross spring pivot
1

Zero adjustment at the adjustment screw (11).

Fig. 3: Functional diagram

Ordering code
Complete order number as required
Version

Order no.: 3812-xxxx

xx

xx

000x

Sensor type
Bulb sensor

1Air sensor

2Sensor for food processing (T-union)

3

Ordering text
Type 3812 Pneumatic Transmitter(order no. 3812-...)

Sensor version
Capillary tube, 3 m

1

Protected capillary tube, 3 m

2Capillary tube, 6 m

3Protected capillary tube, 6 m

4Bulb sensor, fixed

5Measuring span
50 °C

00100 °C

10200 °C11

Output signal
0.2 to 1 bar01

3 to 15 psi

02Connection
G 1/801

1/8 NPT02

Measuring range2–20 to +30 °C

10 to +50 °C

20 to +100 °C

3+50 to +150 °C

40 to +200 °C

5Span 50 °C, lower range value between –40 and +150 °C

6 1)Span 50 °C, lower range value between +150 and +250 °C

7 1)Span 100 °C, lower range value between –40 and +200 °C

8 1)

Span 200 °C, lower range value between –40 and +100 °C

9 1)

Specify the measuring range thatyou require on ordering. The
transmitter will then delivered with thismeasuring range.

1)

T 7575 EN

Table 1: Technical data · All pressure stated as gauge pressure pe in bar
Measuring span

50 °C

100 °C

Measuring range limits

200 °C–40 to +300 °C

Overload limits

350 °C

350 °C

500 °C

SupplySupply air 1.4 ±0.1 bar (20 ±1.5 psi)

Output

0.2 to 1.0 bar/3 to 15 psi
Max. 2 mn³/h

Air output capacity

0.1 mn³/h in steady-state condition

Consumption
Reversing error< 0.3 %

Deviation from terminal-based linearity< 0.6 %

Hysteresis< 0.2 %

Influence

Supply air: < 0.12 %/0.1 bar

Pressure at the sensor< 0.4 %/10 barAmbient temperature< 0.06 %/K< 0.2 %/10 bar< 0.1 %/10 bar< 0.03 %/K

Permissible ambient temperature–40 to +90 °C

Capillary tube length

3 m or 6 m

Table 2: Materials · Material numbers according to DIN EN
Type 3812
Enclosure and coverDie-cast aluminum AlSi12

BellowsBronze

Bellows fixture

BrassDiaphragms

ECO (epichlorohydrine)

Seals and O-rings

Silicone

Sensor

CrNiMo steel 1.4571/1.4404

Sensor filling

Inert gas

Capillary tube

CrNiMo steel 1.4571/1.4404

Clamping flange, screw gland, thermowells

CrNiMo steel 1.4571/1.4404

Dimensions in mm
Standard version

Wall mounting
Ø2053

8297
Ø7NPTG1/81/83001)

704004202712503001)

Ø124251801)

320

143

Ø12Ø17R¾R¾3052

R¾Special version withprotective metal hose

Ø17For installation inT-union according toDIN 11857

NPTG1/8

1/81801)

Air sensor

250356

Installation inT-union according
to DIN 11857

Standard version

Pipe mounting591)

Fig. 4: Dimensions

T 7575 ENNPT
G1/8

1/8

Active sensor lengthOutput

Supply air3

Mounting
All the dimensional diagrams show the standard mounting
position. Other mounting positions may require the correctionof the lower range value.

To ensure accurate measurements, the active bulb length of thesensor must be entirely immersed in the fluid to be measured.
Air connections: two tapped holes 1/8 NPT (optionally, twotapped holes ISO 228 G 1/8)

For versions with capillary tube, the temperature sensor canbe mounted in any position. This version comes supplied witha bracket for wall mounting. Pipe mounting requires a special
mounting bracket (order no. 1,089-0101).

Accessories
Accessories are not included in the scope of transmitter delivery. They need to be ordered separately. Select accessories required
for the operating conditions at the site of installation.
Clamping flange
Clamping flange for wall mounting, e.g. on pressureless vessels, ducts etc.
Order no.: 1090-9547

Screw gland (PN 10) for pressures up to 10 bar*) G ½: order no. 1080-4881
G ¾: order no. 1080-4882

Screw gland (PN 40) for pressures up to 40 bar*) G ½: order no. 1080-4884
G ¾: order no. 1080-4885

Thermowell (CrNiMo steel) with thread (PN 63) for pressures up to 63 bar*) G ½: order no. 1080-4888
G ¾: order no. 1080-4889

Thermowell (CrNiMo steel) for welding (PN 63) for pressures up to 63 bar
Thermowell (CrNiMo steel) with flange DN 25 for PN 40 or PN 100
Details on request
Weld-in version:
Order no.: 1080-4890

Fig. 5: Accessories

Specifications subject to change without notice

T 7575 EN

2024-03-18 · English

Flange:Order no.: 1080-4891 (PN 40)
Order no.: 1080-4892 (PN 100)