/ndg08t_manual_gb

Normdichtetransmitter NDG 08 T

Standard Density Transmitter

NDG 08 T

Operation Manual

RMG Meßtechnik GmbH Otto-Hahn-Strasse 5 · D-35510 Butzbach P.O.Box 280 · D-35502 Butzbach Phone: +49(0)6033/897-0 · Fax: +49(0)6033/897-130

03/99

Reliability in gas supply – single-sourced across the board

NDG 08 T Standard Density Transmitter

Contents Page

Ed. 3/99

Chapter 1

Functional principle

4

Chapter 2

Starting-up the NDG 08 T and terminal diagrams 2.1 Mechanical connection 2.2 Electrical connection 2.3 Starting-up the NDG 08 T 2.4 Checking data entered 2.5 Switch positions of the NDG 08 T 2.6 Terminal assignments

Chapter 3

Construction of the NDG 08 T 3.1 Hardware 3.2 Software 3.3 Selection of functions 3.4 Examples

Chapter 4

5 5 5 5 5 6

7 7 9 9

Options for calculation 4.1 Standard density 4.2 Contents 4.3 Velocity of sound

10 10 11

Chapter 5

Current outputs

12

Chapter 6

Operating the NDG 08 T

Chapter 7

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6.1 Display field 6.2 Key assignments 6.3 Examples

13 13 15

Recalibrating the NDG 08 T

16

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Chapter 8

Specifications 8.1 Electrical data 8.2 Mechanical data 8.3 Metrological data

17 17 17

Chapter 9

Approval of the NDG 08 T

18

Chapter 10

Maintenance

18

Chapter 11

Fault messages 11.1 Operator input errors 11.2 System faults (hardware and software) 11.3 Alarm numbers

19 20 20

Chapter 12

Setup and dimensions

21

Chapter 13

Response times of the NDG 08 T

22

Annex

Assembly instructions for Swagelock connections

24

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter The NDG 08 T standard density transmitter is a combination of the field-proven NDG 08 standard density transducer and a new type of general-purpose transmitter.

Chapter 1

Functional principle

The NDG 08 standard density transducer serves to determine gas densities at standard conditions. The measuring sensor for density used is a tuning fork whose natural frequency is determined by the density of the measuring gas surrounding it.

The standard density transducer has two tuning forks installed in separate measuring chambers. One of these chambers is filled with a reference gas similar to the measuring gas, whereas the measuring gas continuously flows through the second chamber. The tuning forks supply frequencies proportional to the densities to the transmitter. The transmitter serves to process signals and determines the standard density by comparing these frequencies.

The NDG 08 T thus performs the following functions: – The standard density is shown in the display of the NDG 08 T together with its associated current and the channel number.

– The individual contents (volume, mass and mole contents) of a binary gas mixture can be displayed.

– Each of the values displayed can be outputted as a 4 - 20 mA signal due to the 2-wire technology used. This enables processes to be measured, monitored and controlled.

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Chapter 2

Starting-up the NDG 08 T and terminal diagrams

The NDG 08 T standard density transmitter can be installed in hazardous areas. It is fitted in a protective wall cabinet as standard. The cabinet dimensions and the boring diagram for mounting the cabinet can be taken from the drawing on page 21. All gas pipes and cables must be introduced into the cabinet through the flexible rubber grommets. This ensures that the cabinet’s IP protection class is maintained.

2.1 Mechanical connection The NDG 08 T has a gas inlet and a gas outlet.

• The inlet connection A has been designed for 6 mm Swagelok couplings and can be pressurized with a minimum of 4 bar and a maximum of 10 bar.

Please observe the assembly instructions for Swagelok connections enclosed in the annex.

• The gas outlet has been designed for 6 mm Swagelok couplings. The exhaust gas pipe should be directly discharged into the outside or a gathering system. Make sure that there is no backpressure.

• You can now let the measuring gas flow into the NDG 08 T. The inlet pressure regulator is preset at 4 bar. You do not have to make any settings, as the optimum flow was set in the factory.

2.2 Electrical connection • The NDG 08 T is supplied by an EEx i transmitter supply unit. When it is used in a non-hazardous area, it is to be directly supplied with 12-30 V/DC. • The current output can be set at 4 - 20 mA or constant currents of 4, 12 or 20 mA. 2.3 Starting-up the NDG 08 T You can now switch on the voltage supply. The NDG 08 T will need some time to stabilize, until the measured data can be collected at the transmitter.

2.4 Checking data entered The constants and device data were inputted during testing. If it is necessary to change these data, such changes must be made in the computer matrix (see Chapter 6).

2.5 Switch positions of the NDG 08 T The S5 switch must be set to "MESSEN" (MEASURE) and the S6 switch must be set to "BETRIEB" (RUN).

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter 2.6 Terminal assignments Referenzgabel

Meßgabel

Auswerte Erreger Spule Spule

KL1

Auswerte Erreger Spule Spule

PT 1000

1 2 3 4 5 6 7 8 9 10 11 12

L1 L2 + _

1 2 3 4 5 6 7 8 9 10 11 12 +

+

Halten

Kalibrieren

A B

KL2

Example: Line length = 240 m at Ca of 70 nF La 4.2 mH Control cable: LiYCY-2x0.75 mm2 110 nF/1000 m 0.7 mH/1000 m

4

5

6

+

7

8

9

calibrate

3

hold

+

2

supply 4-20 mA

1

+

10

EEx i - connecting box

Hazardous rea Non-hazardous area EEx i transducer supply unit (option)

+

EEx i isolating amplifier (option)

supply

+

+ 4-20 mA

Legend: Referenzgabel: Meßgabel: Auswertespule: Erregerspule: Halten: Kalibrieren: Versorgung:

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Reference tuning fork Measuring tuning fork Evaluating coil Operating coil Hold Calibrate Supply

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Chapter 3

Construction of the NDG 08 T

3.1 Hardware The NDG 08 T has a base board which comprises the following components: 8-bit 80C32L microcontroller EPROM 32 Kbytes EEPROM 512 bytes Frequency measurement max. 32 bits (reciprocal measuring method) A/D converter 15 bits measuring period: 60 ms D/A converter 12 bits Depending on the design, up to 2 digital density amplifiers which amplify the signal coming from the standard density transducer are fitted as additional boards.

1 VOS amplifier Watchdog timer LCD with control panel Serial TTL interface Inputs for measuring/holding/calibrating Functions: "HALTEN" (Hold) = Switch position "HALTEN" (HOLD) and/or input "HALTEN" (HOLD) "KALIBRIEREN" (Calibrate) = "HALTEN" (HOLD) and switch position "KALIBRIEREN" (CALIBRATE) and/or input "KALIBRIEREN" (CALIBRATE) tin > 3 sec tstab < 0.1 sec Imin > 1 mA Umin > 5 V 3.2 Software The computer matrix of the NDG 08 T is divided into different channels which contain all the values and constants which the computer accesses under the appropriate channel number.

Any inputs and changes of current output limits, device constants and gas constants must be made in this matrix.

For recalibration, you must input the specified value of the calibration gas and its relevant limits here.

Also select the desired function via the appropriate mode in this matrix.

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Display of channel assignments of the NDG 08 T A = value displayed M = measured value -- = no function

H = hardware R = calculated value

Channel No. Indication on the display 0 I aus 1 ρn 2 Cn 3 temp 4 anteil 5 f-ρ M 6 f-ρ R 7 min 8 max 9 KK A KM b KR C KC d ρ-n1 E ρ-n2 F kappa1 H kappa2 J Cn1 L Cn2 n mol1 o mol2 P -q Tkal r ρ-Soll U ρ-Delta u ρ-Korr y mode ] Fault indication

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K = constant S = system constant

Mode A/R A/R A/R/M A/R A/R/M A/R/M A/R/M K K K K K K K K K K K K K K K K K K K K

min.

4 0 0.5 -50 0 0 0 0 0 -10000 -10000 -10 -100 0 0

Limits max.

20 10 10000 100 100 10000 10000 10000 100000 10000 10000 10 0 10 10

0.5 0.5 0 0

1.5 1.5 100 100

-50 0 0 -10 0

100 10 100 10 255

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Unit mA kg/m3 m/s °C % Hz Hz k/m3; % k/m3; %

kg/m3 kg/m3

°C kg/m3 % kg/m3

NDG 08 T Manual

NDG 08 T Standard Density Transmitter 3.3 Selection of functions (settable in channel y) The selection table of the various modes is shown below. If you select a specific mode, this will result in a change in the function of the NDG 08 T and the current output in accordance with the mode chosen.

Mode 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Function VOS measurement Density at actual conditions Standard density VOS volume contents VOS mass contents VOS mole contents VOS volume contents VOS mass contents VOS mole contents NDG volume contents NDG mass contents NDG mole contents NDG volume contents NDG mass contents NDG mole contents Standard density NDG volume contents NDG mass contents NDG mole contents NDG volume contents NDG mass contents NDG mole contents

Effect on current output Cn ρb ρn r2 m2 x2 r1 m1 x1 r2 m2 x2 r1 m1 x1 ρn with tkal r2 with tkal m 2 with tkal x2 with tkal r1 with tkal m 1 with tkal x1 with tkal

130-246

No function

247

Erase Kty-offset/ tkquartz/ quartz=500kHz

248 249 250 251 252 253 254 255

Pt-1000 calibrate at 1000 Ω/0°C Spare Spare Spare Calibrate quartz frequency 20 mA constant current 12 mA constant current 4 mA constant current

3.4 Examples ρn

cn

Temp.

Content

Current output

Mode 2

0.8

0

24.02

0

0.5-1.5 kg/m3 = 4-20 mA

Mode 12

0.8

380

24.02

70

65-75%

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= 4-20 mA

NDG 08 T Manual

NDG 08 T Standard Density Transmitter Chapter 4

Options for calculation

On the one hand, the NDG 08 T can determine the velocity of sound and on the other hand, it can determine the volume, mass and mole contents of a binary gas mixture.

As to the latter, the NDG 08 T also calculates the standard density and the velocity of sound of the individual contents.

4.1 Standard density The standard density is calculated as follows: Measured values:

fρm = Frequency of the measuring chamber fρr = Frequency of the reference chamber

τm = τr =

10000 fρm

10000 fρr

ρn = KK ⋅

KM + τm 2 + KC KR + τr 2

KK, KM, KR, KC are device constants.

4.2 Contents The contents of a binary gas mixture are determined as follows: Volume contents

r2 =

ρn1- ρn ρn1- ρn2

r1 = 1 − r 2

Mass contents

m2 = r2 ⋅

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ρn2 ρn

m1 = 1 − m2

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Mole contents

x2 =

r2 ⋅

ρn2 M2

ρn2 ρn1 + r1⋅ r2 ⋅ M1 M2

x1= 1- x2

4.3 Velocity of sound The velocity of sound is calculated as follows from the standard density:

χ = (χ2 - χ1) ⋅ content + χ1 cn =

χ ⋅ pn ρn

where ρn1, ρn2, χ1, χ2, M1, M2 are gas values.

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Chapter 5

Current outputs

A current output of 4 to 20 mA can be determined for each content (volume, mass or mole content) or the standard density. This means for example that the output current depends on the standard density or the volume content or the like.

Examples of possible current outputs of the NDG 08 T: Value Ď n r1 r2 m1 m2 x1 x2

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Example 0.5 to 1.5 kg/m3 70 to 90% 10 to 30% 75 to 85% 15 to 25% 80 to 95% 5 to 20%

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Current output 4 to 20 mA 4 to 20 mA 4 to 20 mA 4 to 20 mA 4 to 20 mA 4 to 20 mA 4 to 20 mA

NDG 08 T Manual

NDG 08 T Standard Density Transmitter Chapter 6

Operating the NDG 08 T RMG Messtechnik

Meßwerte/Daten

Ausgangsstrom (mA)

1

Dichte (kg/m3)

2

3

Schallgeschw. (m/s)

+

Eingabe AnzeigeTest

Legend: Meßwerte / Daten Ausgangsstrom Dichte Schallgeschw.

Anteil Anzeigetest Fehler löschen Fehleranzeige

: : : : : : : :

4

Temp. (°C)

Fehlerlöschen

Anteil (%)

Speichern

FehlerAnzeige

Measured values / datas Output current Density Velocity of sound Contents Display test Reset fault Display fault

6.1 Display field The NDG 08 T has a 2-line display with 8 characters each. Each line is divided into two fields. The first field displays the channel number, while the second field displays the measured values and constants. The top line of the display shows physical values and constants, while the bottom line always shows the output current.

Channel number Display value

1 0

0,8152 9,6543 Current relating to the display value Channel number

6.2 Key assignments In addition, there are four function keys for operating the NDG 08 T. The NDG 08 T has two operating modes, for which the keys provide different functions.

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter "BETRIEB" (RUN) is the first operating mode.

Key assignments

Switch positions of the NDG 08 T Messen (Measure)

Betrieb

KL1

(Run)

Kalibrieren Dichte

Schallgeschw.

(Calibrate) Temp

Anteile

Eingabe (Enter)

L1 L2 +

_

4-20 mA Signal Versorgung (supply 4-20 mA)

Anzeigetest

Fehlerlöschen

Com 1

Fehleranzeige

In this mode, you can directly select the display value for density ("DICHTE"), velocity of sound ("SCHALLGESCHW."), temperature ("TEMP.") or contents ("ANTEIL"). In addition, you can display ("FEHLERANZEIGE") or reset fault(s) ("FEHLER LÖSCHEN") or conduct a display test ("ANZEIGETEST") by pressing the appropriate keys (see illustration above).

"EINGABE" (INPUT) is the second operating mode.

Key assignments

Switch positions of the NDG 08 T Messen (Measure)

Betrieb

KL1

(Run)

Kalibrieren (Calibrate)

+

_

Eingabe

Eingabe (Enter)

L1 L2 +

_

4-20 mA Signal Versorgung

Speicher

(supply 4-20 mA)

Com 1

In this mode, you can input and change values. Press the first two keys to browse in the matrix. Press the "EINGABE" (ENTER) key to activate the entry process and use the "+" and "-" keys to change the values. Then press the "SPEICHERN" (STORE) key to complete the entry process and store the changed values in the matrix.

Inputting and changing values can also be carried out using the COM1 interface of the computer. (To do this, the appropriate interface adapter is required.)

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter 6.3 Examples Example: Changing values •

Set the S6 switch to "EINGABE" (INPUT).

•

Use the "+" "-" keys to select the desired channel.

•

Press the "EINGABE" (ENTER) key to activate the input.

•

Use the "+" "-" keys to set the desired value.

•

Press the "SPEICHERN" (STORE) key to accept the set value.

•

Reset the S6 switch to "BETRIEB" (RUN).

To change a mode, you must proceed in the same way.

Example: Setting the current output •

Set the S6 switch to "EINGABE" (INPUT).

•

Use the "+" "-" keys to select the mode channel.

•

Press the "EINGABE" (ENTER) key to activate the input.

•

Use the "+" "-" keys to set the desired mode (see Chapter 3 Selection of functions)

•

Press the "SPEICHERN" (STORE) key to accept the set mode.

•

Reset the S6 switch to "BETRIEB" (RUN).

Example: Resetting faults •

Press the "TEMP." and "ANTEIL" (CONTENT) keys to display the fault(s).

(This is only possible in "BETRIEB" mode.)

•

Check and clear the fault(s).

•

Use the "SCHALLGESCHW." (VELOCITY OF SOUND) and "TEMP." keys to clear the display. If there is no longer a fault pending, the display will show "GOOD".

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Chapter 7 Recalibrating the NDG 08 T Input the known standard density or velocity of sound of the calibration gas together with their permissible limit values into the matrix of the NDG 08 T. These will be the comparison values for automatic recalibration.

Any gas or gas mixture whose standard density is known and lies within the range of the measuring gas may be used as calibration gas.

Messen

(Measure)

Halten

Betrieb

(Hold)

(Run)

Kalibrieren

Eingabe

(Calibrate)

(Enter)

KL1 _ L1 L2 + 4-20 mA Signal Versorgung (supply 4-20 mA)

Com 1

The NDG 08 T has the two contact inputs "HALTEN" (HOLD) and "KALIBRIEREN" (CALIBRATE). If none of these functions has been selected, the "MESSEN" (MEASURE) function is active. Select the "HALTEN" (HOLD) function before starting calibration, so that the current which has been calculated last will be maintained in the "MESSEN" (MEASURE) function, while the correction value for the standard density will be set to zero.

To recalibrate the NDG 08 T, you must proceed as follows: • Set the S5 switch to "HALTEN" (HOLD).

• Connect the calibration gas.

• After stabilization, you must either actuate the "KALIBRIEREN" (CALIBRATE) switch or contact and hold it for at least 3 seconds.

• The calibration gas is measured and compared with the specified value in the matrix. The difference is determined as offset from the measured value.

• Reconnect the measuring gas.

• Switch back to "MESSEN" (MEASURE). While doing so, the offset value is stored in the matrix under ρ-korr.

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Chapter 8

Specifications (Please observe the electrical data in the certificate of conformity!)

8.1 Electrical data Power supply via intrinsically safe (EExi) supply unit (or 12 to 30 V/DC direct; but only when used in nonhazardous areas) Current outputs

4 to 20 mA - 2-wire technology 4 mA constant current 12 mA constant current 20 mA constant current

Interface

serial, TTL level

8.2 Mechanical data Gas inlet:

6 mm Swagelok pipe connection

Inlet pressure:

pmin pmax

Exhaust gas connection:

6 mm Swagelok pipe connection

Gas consumption:

approx. 20 to 60 standard litres per hour

4 bar 10 bar

8.3 Metrological data Measuring gas:

depending on the calibration of the NDG 08 T; standard: natural gas

Measuring range:

0.4 to 3.5 kg/m3

Measuring error:

≤ +0.2%

Operating temperature:

0 to +50°C

Operating pressure:

4 to 10 bar

Response time:

approx. 30 to 60 sec

Tuning fork frequency:

approx. 1000 Hz

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Chapter 9

Approval of the NDG 08 T

The NDG 08 T standard density transmitter consists of two separately certified devices: − NDG 08 T gas density transmitter (measurement evaluator) II 2 G EEx ib IIC T6 PTB 04 ATEX 2030 − UT01 general-purpose transmitter (electronic module) II 2 G EEx ib IIC T4 PTB 04 ATEX 2029 (see annex)

Chapter 10 Maintenance Basically, the NDG 08 T does not require any maintenance. As with each measuring instrument, you must take care that the device is supplied with clean and dry gas only.

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Chapter 11 Fault messages 11.1 Operator input errors Error number 0 = Iaus 1 = ρ a/n 2 = cn 3 = temperature 4 = anteil (content) 5 = f-cn/ρa/ρn 6 = f-ρ r 7 = min 8 = max 9 = KO 10 = K1 11 = K2 12 = K3 13 = ρ-n1 14 = ρ-n2 15 = kappa1 16 = kappa2 17 = cn1 18 = cn2 19 = mol1 20 = mol2 21 = kappa 22 = Tkal 23 = specified value 24 = limit 25 = correction 26 = mode 27 = ---28 = 4mA-korr 29 = I-korr 30 = R-korr 31 = offset 32 = Kty 50 = calibrate 60 = cn/ρ min 61 = cn/ρ max

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Error Min /max limit Min /max limit Min /max limit Limit -50/100°C Min /max limit Limit 0 to10 kHz Limit 0 to10 kHz Limit Limit Limit Limit Limit Limit Limit Limit Limit Limit Limit Limit Limit Limit Limit Limit Limit Limit Limit Limit ---------Limit only via V24 Limit only via V24 Limit only via V24 Error adjustment auto Error adjustment auto Min/max limit of KNR "U" Limit Limit

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter 11.2 System faults (hardware and software) 100 = Reset/watchdog 101 = AD measurement 102 = FD measurement 103 = Time-out 104 = Time-out 105 = Case 106 = Quartz frequency 107 = Polarity 108 = Case 109 = Time-out 110 = Time-out 111 = Time-out 112 = Case 113 = Overflow-String 114 = Case 115 = Busy 116 = Case 254 = Stack error

No end-of-measurement signal No end-of-measurement signal EEPROM EEPROM Module-CONST Min/max limit 499-501 kHz Module-analog measurement Module-analog measurement Module-interface Module-interface Module-display Module-display Module-display Module-D/A conversion EEPROM Module-CONST System error

11.3 Alarm numbers 02 = 1-out-of-2 comparison idata/EEPROM 03 = 1-out-of-2 comparison and RAM defective 04 = RAM defective idata 08 = Ram defective xdata

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Chapter 12 Setup and dimensions

Air outlet

20

NDG

20

Electronic transmitter control

Ø11

Pressure regulator

RMG Messtechnik

1 2

Pressure regulator pF max. = 10 bar

0,8453 9,6784

Filter

Air inlet 20

Ø11

20

C Ex-d heater with thermostat, 10°C fixed value A 890

A- Measuring gas inlet / 6 mm pipe with Swagelok connection B- Exhaust gas / 6 mm pipe with Swagelok connection C- Voltage supply / signal outputs

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Chapter 13 Response times of the NDG 08 T The response times of the NDG 08 T have been determined in trials. To this end, the NDG 08 T was alternatively supplied with methane and nitrogen and on the other hand, with methane and natural gas. The first trial was conducted with a switching point directly upstream of the NDG 08 T, and the second trial was conducted with a switching point before a supply line with a length of 6 m (dia. 6 mm; wall thickness 1 mm; pipe volume 75,396 mm3 = 0.0754 litres).

Density values: Natural gas: Methane: Nitrogen:

0.8 kg/m3 0.7175 kg/m3 1.2505 kg/m3

Pressure values:

Inlet pressure before switching point: 6 bar Inlet pressure of measuring chamber: 3 bar Reference chamber: 2 bar

Time was measured from switching until almost 100% of the new value was reached.

In the tables below, time is indicated in seconds.

1st trial: Gas switching directly upstream of the NDG 08 T Methane

⇒

Nitrogen

Measurements 1 2 3 Nitrogen

⇒

90% 24 23 27

95% 31 32 32

90% 50 50 45 44

95% 61 61 62 55

Methane

Measurements 1 2 3 4

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50% 12 11 13

50% 22 21 16 21

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Methane

⇒

Natural gas

Measurements 1 2 3 Natural gas ⇒

50% 15.5 23.5 13

90% 31 31 32

95% 41 41 40

90% 43 45 48

95% 53 57 51

Methane

Measurements 1 2 3

50% 16 18 19

2nd trial: Gas switching before a supply line (length 6 m) Methane

⇒

Nitrogen

Measurements 1 2 Nitrogen

⇒

⇒

50% 51 54

90% 78 78

95% 90 90

50% 29 30

90% 44 46

95% 56 54

90% 53 52

95% 66 66

Methane

Measurements 1 2

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95% 49 49

Natural gas

Measurements 1 2 Natural gas ⇒

90% 40 42

Methane

Measurements 1 2 Methane

50% 28 33

50% 28 27

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NDG 08 T Manual

NDG 08 T Standard Density Transmitter Annex

ASSEMBLY INSTRUCTIONS FOR PIPE CONNECTIONS INITIAL ASSEMBLY Cut pipe perpendicularly and remove fins. Insert pipe into fitting until stop is reached.

Tighten nut with fingers only.

Prior to tightening the SWAGELOK nut, mark it in the 6 o'clock position.

Then tighten nut with 1¼ turns* until marking reaches the 9 o'clock position.

* For pipe connections sized 2, 3, 4 mm or 1/16", 1/8", 3/16", you must tighten the nut with a ¾ turn during initial assembly.

REASSEMBLY Removed fitting

Insert pipe with clamping rings into fitting until stop is reached.

Tighten nut with fingers only, then use wrench to tighten it with approximately ¼ turn.

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NDG 08 T Manual