ducer with Root Extracted Output Type P 82 R

halstrup 

wa cher 

halstrup-walcher GmbH 

Stegener Straße 10 

D-79199 Kirchzarten 

Phone: [49] (0) 7661 /39 63-0 

Fax: [49] (0) 7661 /39 63 99 

e-mail: info@halstrup-walcher.de 

Internet: www.halstrup.de 

Operating Instructions for the Pressure Transducer 

with Root Extracted Output Type P 82 R 

List of contents 

1 General.........................................................................................................................2 

2 Safety notices ...............................................................................................................2 

3 Installation ....................................................................................................................2 

4 Electrical connections ...................................................................................................3 

5 Analogue outputs..........................................................................................................4 

6 Calibration of the zero point..........................................................................................5 

7 Adjustment of the creeping suppression volume ..........................................................5 

8 What to do in the event of a fault ..................................................................................6 

9 Technical data (in accordance with DIN16086) ............................................................7 

10 Dimensional drawing (not to scale)...............................................................................9

1 General 

The pressure transducer P 82 R is a pneumatic electrical sensor designed to measure pressure 

(positive gauge pressure or differential pressure). Due to the root extracted output characteristic 

curve this particular transducer is often employed within air conditioning and ventilation technology 

in which it is used to measure volume flow or the velocity of air in a ventilation shaft. The 

key part is a pressure measuring canister which contains a diaphragm made of beryllium bronze. 

Differences in pressure between the two chambers in the pressure canister cause the diaphragm 

to deflect correspondingly. These deflections are measured via an inductive displacement transducer 

without any contact taking place. 

2 Safety notices 

Please read before use 

The electrical connections may only be made by suitably qualified personnel. 

Please observe the rated power supply (see equipment label). 

Observe the permitted pressure ranges (measuring ranges). 

Observe the storage and transport temperature as well as the operating temperature. 

Do not allow the instrument to be exposed to direct sunlight as errors caused by the sun's 

influence will occur. 

The measuring cell is not suitable for measuring aggressive gases. 

Do not close off the pressure ports during transportation (barometric pressure changes may 

otherwise damage low range instruments). 

Please do not use air lines or exhalation as a means of functional testing. 

Opening of the instrument, improper handling as well as non-compliance with the operating 

instructions renders the guarantee as null and void. 

3 Installation 

The pressure transducer P 82 R is a precision measuring instrument and should, in spite of its robustness, 

be treated with care. The installation in the immediate vicinity of heat and radiation 

sources, such as radiators for example, should be avoided as inaccurate readings may otherwise 

be obtained. For best results the instrument should be mounted vertically on a wall free from 

vibration. To prevent any condensation entering the pressure measuring cell the transducer must 

be mounted so that the pressure ports are facing downwards. The hoses are to be attached as 

follows: for positive gauge pressure ⊕ and negative gauge pressure - . 

halstrup-walcher GmbH, 79199 Kirchzarten Operating instructions P 82 R Page 2 of 9

4 Electrical connections 

Not all components are shown 

U0 

UA 

I0 

S 

SMU 

lin 

C7 

IA 

D8 

D9 

SI 

√ 

+ 1 2 3 4 11 13 

Fig. 1 

pin 

power supply 

pin 

analogue output 

11 

24/115/230 V~ 50/60 Hz 

1 

0...10 V 

13 

24/115/230 V~ 50/60 Hz 

2 

ground connection (GND) 

11 


3 

0...20 mA / 4...20 mA 

13 

+20,5 V...28,5 VDC 

4 


Observe rated power supply (see equipment label) 

Observe additional connection plan enclosed in housing lid. 


5 Analogue outputs 

The transducer's outputs are protected against short circuit. Instruments with a direct current 

power supply are protected against reverse polarity of the supply voltage. 

The inadvertent connection of the power supply 

onto the output connections leads to permanent 

damage of the transducer. 

The flow speed or volume flow can be obtained from the so called differential pressure producer. 

The differential pressure ∆p which occurs at the producer is registered by the pressure transducer 

type P 82 R. The following relationship is true: 

v ∼ q v ∼ √∆p 

v.....flow speed 

q v ...volume flow 

∆p...measured differential pressure 

The output of a P 82 R with a square root characteristic ("root extracted “) is directly 

proportional to the flow speed / volume flow. Three possible output types are available: 

Voltage output 0...10 V 

U 

10 V 

0 V 

U root 

U lin 

100% p 

U root = √ 10 V • √ U lin 

Current output 0...20 mA 

Current output 4...20 mA 

I 

I 

20 mA 20 mA 

I root 

I root 

I lin I root = √ 20 mA • √ I lin I l in I root = √ 16 mA • √ I lin - 4 mA + 4 mA 

4 mA 

0 mA 

100 % p 100 % P 

with the aid of the slide switch S (see fig. 1) it is possible to change the characteristic from "rooted" 

to "linear": Please note that the rooted position is indicated in German (radiziert) 

linear 

rooted √ 

Switch S 


6 Calibration of the zero point 

Please note that after switching on the transducer requires a warm up 

time of approximately 30…60 minutes. During this time the output signal may 

be unstable. 

Before calibrating set the slide switch S to "Linear". 

The trimmer SMU (creeping suppression volume) is to be turned fully anticlockwise. 

After the transducer's warm up time has passed the zero point can be calibrated using the trimmer 

U0 or trimmer I0 with current output (see fig. 1) 

Here it is important to ensure that no pressure is connected to the transducer. Likewise the pressure 

hoses are also to be disconnected. 

After calibration of the zero point the switch S must be placed back in the "rooted √" position. 

7 Adjustment of the creeping suppression volume 

U/I 

0...10% 100% p 

The creeping suppression volume provides a means of suppressing the transducer's output in 

spite of a pressure being present, in other words the output will be held at zero. The creeping suppression 

volume can be set with the aid of the trimmer SMU between a value of 0…10 % of the 

measuring range. The use of this facility is advisable in certain applications as the repeatability 

of readings within the region of very small flow speeds / volume flows is almost unachievable. 

Using the creeping suppression volume limits the transducer's measuring 

range in the lower scale depending on the setting of between 0…10 %. The 

output will be held at "0" in spite of pressure being present. 


8 What to do in the event of a fault 

description of fault possible cause cure 

no output signal 

• power supply not connected 

• connect the correct power 

supply 

output signal remains 

constant in spite of 

changing pressure 

faulty output signal 

zero point can no longer 

be adjusted with U0 / I0 

• incorrect power supply 

connected 

• fuse blown 

• defective input protection diode 

• defective output protection diodes 

• pressure connections crossed 

over 

• creeping suppression volume set 

too high 

• defective output protection diode 

• defective pressure measurement 

canister 

• with current output load to large 

• with voltage output load 

resistance to small 

• defective pressure measurement 

canister 

• connect the correct power supply 

(see rating label) 

• replace fuse SI (type TR5 200 mAT 

from the company Wickmann) 

• replace diode D12( type ZPY 33) 

• replace D8 / D9 (type ZPY18) 

• connect pressure in accordance 

with “3. Installation“ 

• turn the trimmer SMU anti-clock 

wise until the output 

signal ≠ 0 V / 0/4 mA 

• replace D8 / D9 (type ZPY18) 

• return instrument for repair at 

factory 

• observe maximum load of 500 Ω 

• minimum load resistance of 5 kΩ 

• return instrument for repair at 

factory 

Table 2 

Never perform a functional test using exhalation as this can lead to 

permanent damage of the pressure measuring cell. 

Simple functional test of the transducer: 

Connect a hose to the pressure port for positive gauge pressure + . Taking the hose 

between thumb and fore finger, squeeze it and then carefully move the volume of air 

trapped within the hose in the direction of the transducer. 


9 Technical data (in accordance with DIN16086) 

Manufacturer: 

Type: 

Calibrated pressure 

forms: 

Measuring principle: 

halstrup-walcher GmbH 

P 82 R 

positive gauge pressure of non-aggressive gases 

Deflection of a copper-beryllium diaphragm is registered 

via an inductive pick-up 

Input magnitudes: 

Measuring ranges: 

Excess pressure: 

Maximum system 

pressure: 

0…100 Pa to 0…20 kPa (others upon request) 

5 times the end of scale value 

100 kPa 

Dead volume: 

approx. 2000 mm 3 (measuring range ≥ 250 Pa) 

approx. 9000 mm 3 (measuring range < 250 Pa) 

Control volume: 

200 mm 3 maximum 

Materials in contact with measured medium see annex A 

Output characteristics of the pressure sensor: 

Temperature coefficient 

of the zero signal: 

0,4 % / 10 K (within the range + 10 °C to + 50 °C) 

Temperature coefficient 

of the output span: 0,4 % / 10 K (within the range + 10 °C to + 50 °C) 

Deviation of the output 1 % of the output span, rooted characteristic curve 

characteristic curve: (best straight line) 

Hysteresis: 

Warm up time: 

Response time: 

Load resistance R L : 

Load R B : 

Power supply 

Supply voltage: 

< 0,1 % of the output span 

approx. 30 min. 

20 ms, 1s, 2s or 5s optional 

R L ≥ 5 kΩ (voltage output) 

R B < 500 Ω (current output) 

Power consumption: 

Environmental conditions 

Nominal temperature range: + 10 °C…+ 50 °C 

Operating temperature 

range: 0 °C…+ 60 °C 

Storage temperature range: - 10 °C…+ 70 °C 

24 V = + 20 % / - 15 % filtered permitted ripple 1000 mV 

24 V / 115 V / 230 V ~ + 6 % / - 15 % 50 / 60 Hz 

0,9 W 


EMC (electro-magnetic 

compatibility): corresponds to EN 50 081 part 1 and EN 50 082 

part 1 

Mechanical data 

Pressure connections: ∅ 6,5 mm for hose with a nominal width of 5 mm 

Electrical connection: screwed clamps for cable up to ∅ 2,5 mm 

Orientation of installation: vertical (for horizontal installation please mention on 

ordering, otherwise zero point to be calibrated by user) 

Housing dimensions: (B x L x H): 120 x 122 x 75 mm 

Weight: 

0,8 kg 

Enclosure protection: IP 54 

Annex A: Materials in contact with measured medium 

- Beryllium bronze CuBe2 - Araldite CY236 / HY988 

- Mu-metal (nickel compound) - Loctite 242e 

- Brass CUZn39Pb3 - Carbonised iron 

- Aluminium AlCuMgPb / AlMg3 - KEL (FKM: Fe[Co]5 

- Silicon (tubing) - Wepuran Wu 4457/51 

- (PTBP) - UHU-plus endfest ® 300 

Options 

• 3½ digit LCD-display 

• 4½ digit LCD-display 

• certificate of calibration (issued by the German 

Calibration Service {DKD}) 

• locally issued certificate of linearity • wetted components silicone free 

• damping of the output signal up to 5 s 


10 Dimensional drawing (not to scale) 

Fig. 2 

- subject to technical alterations - 

7100.001874 REV C P82R_E.DOC Su/km 26 October 2001

ducer with Root Extracted Output Type P 82 R

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