WIKA S-20 — حساس ضغط

Name: حساس ضغط
Brand: WIKA
SKU: S-20
Price: 351.03 EUR
Availability: BackOrder

الأسئلة والأجوبة

ما هي مجالات قياس الضغط المتوفرة في طراز S-20؟

تتراوح المجالات من 0 ... 0.4 bar إلى 0 ... 1,600 bar، وتتوفر أيضًا نطاقات مطلقة مثل 0 ... 0.4 bar abs. و0 ... 40 bar abs.، ونطاقات تفريغ/ضغط تصل إلى -30 ... 600 inHg.

ما دقة هذا الحساس؟

فئة الدقة هي 0.125 % BFSL وفقًا للمعيار IEC 61298-2، مع خطأ حراري منخفض ودرجة ضبط حراري قابلة للاختيار.

ما وصلات العملية المتاحة؟

تشمل الخيارات G 1/4 A، G 1/2 A، G 1/2 B، M14 x 1.5، M20 x 1.5، 1/2 NPT، R 1/4، PT 1/2، 7/16-20 UNF-2A O-ring BOSS وغيرها — ما مجموعه 18 وصلة مختلفة.

ما الوسائط التي يتحملها الحساس؟

الأجزاء الملامسة للوسط مصنوعة من 316L أو Elgiloy® (2.4711)، مع خيارات حشو من NBR وFPM/FKM وEPDM والنحاس والستانلس ستيل، بما يناسب الوسائط العدوانية والإصدارات الخاصة.

ما مدى درجات الحرارة المسموح بها؟

يمكن للوسط أن يصل إلى +200 °C كحد أدنى -40 °C، بينما تعمل البيئة المحيطة ضمن النطاق -40 … +125 °C.

ما إشارات الخرج والتغذية الكهربائية؟

الخرج متاح كتيار 4...20 mA أو 20...4 mA أو جهود DC 0...10 V وDC 0...5 V وDC 1...5 V وDC 0.5...4.5 V وDC 1...6 V وDC 10...0 V، مع تغذية DC 8...36 V عبر وصلة DIN EN 175301-803 A الزاويّة.

هل يحمل الحساس شهادات لمناطق الانفجار؟

لا تتضمن البيانات المتوفرة شهادات حماية من الانفجار؛ الشهادات المذكورة هي CE وEAC وRoHS فقط.

ما الذي يميّز S-20 عن الطرازات المجاورة؟

يجمع S-20 بين دقة عالية (0.125 % BFSL) وخطأ حراري منخفض مع تنوع تهيئة هائل — أكثر من مليار نسخة عبر مجالات القياس وإشارات الخرج ووصلات العملية — ويُسلَّم بكميات صغيرة بدءًا من قطعة واحدة.

التعريف

الطراز	S-20
النوع الفرعي	Pressure transmitter

نطاق القياس

نطاق الضغط

0…1600 bar · 0…0.4 bar · 0…10 bar · 0…1000 bar · 0…40 bar · 0…600 bar · 0…0.4 bar abs. · 0…40 bar abs. · -30…0 inHg · -30…600 inHg

دقة القياس

فئة الدقة	0.125 % BFSL
معيار الدقة	IEC 61298-2

ظروف العملية

وصلة العملية	G 1/4 AG 1/2 AM14 x 1.5G 1/2 BG 1/2 femaleM12 x 1.5M20 x 1.51/2 NPT7/16-20 UNF-2A O-ring BOSS9/16-18 UNF-2A O-ring BOSSR 1/4R 3/8R 1/2PT 1/4PT 3/8PT 1/2M16 x 1.5 female9/16-18 UNF, female F250-C
درجة حرارة العملية	−40…+200 °C

الخصائص الكهربائية

إشارة الخرج	4...20 mA · 20...4 mA · DC 0...10 V · DC 0...5 V · DC 1...5 V · DC 0.5...4.5 V · DC 1...6 V · DC 10...0 V
التغذية	DC 8...36 V
وصلة كهربائية	Angular connector DIN EN 175301-803 A

المواد

مادة العلبة	Stainless steel
مادة الأجزاء الملامسة	316L, Elgiloy® (2.4711)
مادة الإحكام	NBR, FPM/FKM, EPDM, Copper, Stainless steel

بيئة التشغيل

حرارة المحيط	−40…+125 °C
تصنيف IP	IP65
الوزن	0.15 kg

الشهادات والموافقات

الشهادات

CEEACRoHS

تفاصيل إضافية

لغات ورقة البيانات

جداول من ورقة البيانات

Accuracy specifications	Non-linearity ≤ ±0.5 %of span	Non-linearity ≤ ±0.25 %of span	Non-linearity ≤ ±0.125 %of span 1)
Non-linearity per BFSL per IEC 61298-2	≤ ±0.5 %of span	≤ ±0.25 %of span	≤ ±0.125 %of span
Non-linearity per terminal method per IEC 61298-2	≤ ±1 %of span	≤ ±0.5 %of span	≤ ±0.25 %of span
Accuracy at adjustment temperature	→ See 'Max. measured error per IEC 61298-2'
Max. measured error per IEC 61298-2	≤ ±1 %of span	≤ ±0.5 %of span	≤ ±0.25 %of span

Further details on: accuracy specifications

Non-repeatability per IEC 61298-2	≤ 0.1 %of span
Zero point error	■ ≤ ±0.2 %of span, factory-set ■ ≤ ±0.1 %of span, factory-set 1)
Temperature hysteresis	≤ 0.1 %of span at > 80 °C [176 °F]
Long-term drift per IEC 61298-2	■ ≤ ±0.1 %of span ■ ≤ ±0.2 %of span (with special measuring ranges and measuring ranges < 1 bar [<15 psi])
Temperature error (for adjustment temperature 15 ... 25 °C [59 ... 77 °F])	→ See chart 'Temperature error'
For measuring ranges < 1 bar [<15 psi], special measuring ranges and instruments with an increased overpressure limit, the respective temperature error increases by 0.5 %of span
Adjustment temperature	■ 15 ... 25 °C [59 ... 77 °F] ■ 4 °C ±5 °C [39.2 °F ±9 °F] ■ 40 °C ±5 °C [104 °F ±9 °F] ■ 60 °C ±5 °C [140 °F ±9 °F] ■ 80 °C ±5 °C [176 °F ±9 °F]
Additional zero point error depending on the mounting position for measuring ranges ≤ 1 bar [≤15 psi]
Mounting position 180°, vertical, top process connection	≤ 1 mbar [≤ 0.015 psi]
Mounting position 90°, horizontal, lateral process connection	≤ 0.6 mbar [≤ 0.009 psi]
Reference conditions	Per IEC 61298-1

bar
0 ... 0.4	0…40
0 ... 0.6	0…60
0…1	0 …100
0 …1.6	0 …160
0 …2.5	0 …250
0…4	0 …400
0…6	0 …600
0…10	0 …1,000
0…16	0 …1,600
0…25	-

bar abs.

0 …0.4	0…6
0 …0.6	0…10
0…1	0…16
0 …1.6	0…25
0 …2.5	0…40
0…4	-

عرض الكل (20)

psi
0…10	0 …600
0…15	0 …750
0…25	0 …1,000
0…30	0 …1,500
0…50	0 …2,000
0…60	0 …3,000
0 …100	0 …4,000
0 …150	0 …5,000
0 …160	0 …6,000
0 …200	0 …7,500
0 …250	0 …10,000
0 …300	0 …15,000
0 …400	0 …20,000
0 …500	-

psi abs.

0…10	0 …150
0…15	0 …160
0…25	0 …200
0…30	0 …250
0…50	0 …300
0…60	0 …400
0 …100	0 …500

bar
-0.4…0	-1…+5
-0.6…0	-1…+9
-1…0	-1 …+15
-1 …+0.6	-1 …+24
-1 …+1.5	-1 …+39
-1…+3	-1 …+59

psi
-30 inHg ... 0	-30 inHg ...+100
-30 inHg ...+15	-30 inHg ...+160
-30 inHg ...+30	-30 inHg ...+200
-30 inHg ...+45	-30 inHg ...+300
-30 inHg ...+60	-30 inHg ...+500

Further details on: measuring ranges
Units	■ bar ■ psi ■ kg/cm² ■ MPa ■ kPa
Maximum working pressure	→ Corresponds to the upper measuring range value / measuring range full scale value → Any permanent operation above the maximum working pressure is not permissible
Special measuring ranges	From 0 ... 0.4 to 0 ... 1,600 bar [0 ... 10 to 0 ... 20,000 psi] available on request. Special measuring ranges have an increased long-term drift and higher temperature errors.
Overpressure limit	The overpressure limit is based on the measuring range. Depending on the selected process connection and the seal, restrictions in overpressure limit can result. A higher overpressure limit will result in a higher temperature error.
bar	Measuring ranges ≤ 16 bar	3 times
Measuring ranges > 16 bar	2 times
Measuring range 1,000 bar	1.45 times
Measuring ranges > 1,000 bar	1.25 times
bar abs.	Measuring ranges ≤ 16 bar abs.	3 times
Measuring ranges > 16 bar abs.	2 times
Measuring range 40 bar abs.	1.5 times
psi	Measuring ranges ≤ 300 psi	3 times
Measuring ranges > 300 psi	2 times
Measuring ranges 600 psi, 1,000 psi, 1,500 psi, 4,000 psi, 6,000 psi, 10,000 psi	1.7 times
Measuring range 15,000 psi	1.45 times
Measuring ranges > 15,000 psi	1.25 times
psi abs.	Measuring ranges ≤ 300 psi abs.	3 times
Measuring ranges > 300 psi abs.	2 times
Measuring range 500 psi abs.	1.5 times
Vacuum resistance	Yes
Leakage rate	■ < 510 -3 mbarl/s -6 1) 2)

Process connection

Standard	Thread size	Max. measuring range	Overpressure limit	Pressure port	Seal
DIN EN ISO 1179-2	G¼A 1)	600 bar [7,500 psi]	858 bar [12,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in] ■ 6 mm[0.24 in] 2)	■ NBR ■ FPM/ FKM ■ EPDM
	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	■ FPM/ FKM
G1/2 A	600 bar [7,500 psi]	858 bar [12,440 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in] ■ 12 mm[0.48 in] 2)	■ NBR ■ FPM/ FKM
DIN EN ISO 9974-2	M14 x 1.5	600 bar [7,500 psi]	858 bar [12,440 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	■ NBR ■ FPM/ FKM ■ EPDM
EN 837	G1/8 B	400 bar [5,000 psi]	572 bar [8,290 psi]	■ 2.5 mm[0.1 in]	■ Copper
G¼B 1)	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	■ Copper ■ Stainless steel
G¼, female	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in]	-
G3/8 B	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	■ Copper ■ Stainless steel ■ Without
G1/2 B 1)	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	■ Copper ■ Stainless steel ■ Without
DIN 16288	M12 x 1.5	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	■ Copper ■ Stainless steel ■ Without
M20 x 1.5	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	■ Copper ■ Stainless steel ■ Without
ANSI/ASME B1.20.1	1/8 NPT	400 bar [5,000 psi]	572 bar [8,290 psi]	■ 2.5 mm[0.1 in]	-
¼NPT	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in] ■ 6 mm[0.24 in] 2)	-
¼NPT, female	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in]	-
1/2 NPT 1)	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in] ■ 12 mm[0.48 in] 2)	-
SAE J514	7/16-20 UNF-2A O-ring BOSS	600 bar [7,500 psi]	858 bar [12,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	■ NBR ■ FPM/ FKM
7/16-20 UNF-2A 74°	800 bar [10,000 psi]	1,144 bar [16,590 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	-
9/16-18 UNF-2A O-ring BOSS	600 bar [7,500 psi]	858 bar [12,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	■ NBR ■ FPM/ FKM

Process connection

Standard	Thread size	Max. measuring range	Overpressure limit	Pressure port	Seal
ISO 7	R¼ 1)	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	-
R 3/8	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	-
R 1/2	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	-
KS	PT¼ 1)	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	-
PT 3/8	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	-
PT 1/2	1,000 bar [15,000 psi]	1,480 bar [21,400 psi]	■ 2.5 mm[0.1 in] ■ 0.3 mm[0.01 in] ■ 0.6 mm[0.02 in]	-
Process connection > 1,000 bar [> 15,000 psi]
-	M16 x 1.5 female	1,600 bar [20,000 psi]	2,288 bar [33,180 psi]	2.5 mm[0.1 in]	-
-	9/16-18 UNF, female F250-C	1,600 bar [20,000 psi]	2,288 bar [33,180 psi]	2.5 mm[0.1 in]	-
ANSI/ASME B1.20.1	1/2 NPT	1,600 bar [20,000 psi]	2,288 bar [33,180 psi]	2.5 mm[0.1 in]	-
EN 837	G1/2 B	1,600 bar [20,000 psi]	2,288 bar [33,180 psi]	2.5 mm[0.1 in]	Without
DIN 16288	M20 x 1.5	1,600 bar [20,000 psi]	2,288 bar [33,180 psi]	2.5 mm[0.1 in]	Without

Further details on: process connection

Max. measuring range	→ See table 'Process connection'
Overpressure limit	→ See table 'Process connection'
Seal	→ See table 'Process connection'
Pressure port diameter	→ See table 'Process connection'
Possible restrictions	Depending on the choice of seal at the process connection, there may be restrictions in the permissible temperature range
NBR	-30 ...+100 °C [-22 ...+ +212 °F]
FPM/FKM	-40 ...+200 °C [-40 ...+392 °F]
EPDM	-40 ...+125 °C [-40 ...+257 °F]
Copper	-40 ...+200 °C [-40 ...+392 °F]
Stainless steel	-40 ...+200 °C [-40 ...+392 °F]

Output signal
Signal type
Current (2-wire)	■ 4 ...20mA ■ 20 ...4mA
Voltage (3-wire)	■ DC 0 ...10V ■ DC 0 ...5V ■ DC 1 ...5V ■ DC 0.5 ...4.5V ■ DC 1 ...6V DC 10 ...0V
Ratiometric (3-wire)	DC 0.5 ...4.5V
Load in Ω
Current (2-wire)	≤ (auxiliary power - 7.5 V) / 0.023 A
Voltage (3-wire)	> maximum output signal /1mA
Ratiometric (3-wire)	> 4.5k
Signal damping	See table 'Further details on: output signal'
Signal clamping
Output signal 4 ...20mA	Zero point	■ 3.6mA ■ 3.8mA ■ 4.0mA
	Full scale	■ 20mA ■ 21.5mA ■ 23mA
Output signal DC 0 ...10V	Full scale	■ DC 10V ■ DC 11.5V
Voltage supply
Auxiliary power	Output signal 4 ...20mA	DC 8 ...36V
	Output signal 20 ...4mA	DC 8 ...36V
	Output signal DC 0 ...10V	DC 12 ...36V
	Output signal DC 0 ...5V	DC 8 ...36V
	Output signal DC 1 ...5V	DC 8 ...36V
	Output signal DC 0.5 ...4.5V	DC 8 ...36V
	Output signal DC 1 ...6V	DC 9 ...36V
	Output signal DC 10 ...0V	DC 12 ...36V
	Output signal DC 0.5 ...4.5V ratio	DC 5V ±10%
	→ With cULus approval, limited to max.DC 35V
Current supply	Current (2-wire)	Signal current, max.25mA
	Voltage (3-wire)	Max.12mA
Dissipation loss	Current (2-wire)	828 mW(22 mW/K derating of dissipation loss at ambient temperatures ≥ 100 °C [≥ 212 °F])
	Voltage (3-wire)	432mW
Overvoltage resistance	DC 40V
Dynamic behaviour
Settling time per IEC 61298-2	→ See table 'Further details on: output signal'
Switch-on time	150 ms
Start-up drift	5 s (60 s with optional zero point adjustment 0.1 %)

Further details on: output signal

Signal type	Settling time per IEC 61298-2	Signal damping
	3 dB limit frequency 500 Hz	3 dB limit frequency
Current (2-wire)	3 ms	1 ms	■ 10 ms ■ 50 ms
Voltage (3-wire)	2 ms	1 ms	■ 100 ms ■ 500 ms ■ 1,000 ms
Ratiometric (3-wire)	2 ms	1 ms	■ 2,500 ms ■ 5,000 ms

Electrical connection

Connection type	IP code 1)	Wire cross- section	Cable diameter	Cable material	Permissible temperature
Angular connector DIN EN 175301-803 A 2)
With mating connector	IP65	Max. 1.5 mm²	6 ...8mm	-	-30 ...+100 °C [-22 ...+212 °F]
With mating connector (conduit)	IP65	Max. 1.5 mm²	-	-	-30 ...+100 °C[-22 ...+212 °F]
With mating connector with moulded cable	IP65	3 x 0.75 mm²	6mm	PUR	-30 ...+100 °C (cULus: -25 ...+85 °C) [-22 ...+212 °F (cULus: -4 ...+185 °F)]
With mating connector with moulded cable, shielded	IP65	6 x 0.5 mm²	6.8mm	PUR	-25 ...+85 °C [-4 ...+185 °F]
Angular connector DIN EN 175301-803 C 2)
With mating connector	IP65	Max. 0.75 mm²	4.5 ...6mm	-	-30 ...+100 °C [-22 ...+212 °F]
Circular connector M12 x 1, 4-pin 2)
Without mating connector	IP67	-	-	-	-30 ...+100 °C [-22 ...+212 °F]
With straight mating connector with moulded cable	IP67	3 x 0.34 mm²	4.3mm	PUR	-25 ...+80 °C [-4 ...+176 °F]
With straight mating connector with moulded cable, shielded	IP67	3 x 0.34 mm²	5.5mm	PUR	-25 ...+80 °C [-4 ...+176 °F]
With angled mating connector with moulded cable	IP67	3 x 0.34 mm²	4.3mm	PUR	-25 ...+80 °C [-4 ...+176 °F]
Circular connector M12 x 1, 4-pin, metal
Without mating connector	IP67	-	-	-	-40 ...+125 °C (cULus: +85 °C) [-40 ...+257 °F (cULus: +185 °F)]
With straight mating connector with moulded cable	IP67	3 x 0.34 mm²	4.3mm	PUR	-25 ...+80 °C [-4 ...+176 °F]
With straight mating connector with moulded cable, shielded	IP67	3 x 0.34 mm²	5.5mm	PUR	-25 ...+80 °C [-4 ...+176 °F]
With angled mating connector with moulded cable	IP67	3 x 0.34 mm²	4.3mm	PUR	-25 ...+80 °C [-4 ...+176 °F]
Bayonet connector, 6-pin	IP67	-	-	-	-40 ...+125 °C [-40 ...+257 °F]
Field case	IP6K9K	-	7 ...13mm	-	-25 ...+100 °C [-4 ...+212 °F]

Electrical connection

Connection type	IP code 1)	Wire cross- section	Cable diameter	Cable material	Permissible temperature
Cable outlet
Cable outlet IP67	IP67	3 x 0.34 mm²	5.5mm	PUR	-30 ...+100 °C [-22 ...+212 °F]
Cable outlet 1/2 NPT conduit	IP67	6 x 0.35 mm²	6.1mm	PUR	-30 ...+100 °C (cULus: +90 °C) [-22 ...+212 °F (cULus: +194 °F)]
Cable outlet IP68	IP68	6 x 0.35 mm²	6.1mm	PUR	-30 ...+125 °C (cULus: +90 °C) [-22 ...+257 °F (cULus: +194 °F)]
Cable outlet IP68, FEP	IP68	6 x 0.39 mm²	5.8mm	FEP	-40 ...+125 °C (cULus: +105 °C) [-40 ...+257 °F (cULus: +221 °F)]
Cable outlet IP6K9K	IP6K9K	6 x 0.35 mm²	6.1mm	PUR	-30 ...+125 °C (cULus: +90 °C) [-22 ...+257 °F (cULus: +194 °F)]

Further details on: electrical connection

Connection type	→ See table 'Electrical connection'
Wire cross-section	→ See table 'Electrical connection'
Cable diameter	→ See table 'Electrical connection'
Pin assignment	→ See 'Maximum permissible medium temperature'
Ingress protection (IP code) per IEC 60529	→ See table 'Electrical connection'
Cable length	■ 2m ■ 5m ■ 6 ft ■ 15 ft
Assembly of the cable outlets
Cable outlet IP67	■ Unfinished wire ends ■ Tinned wire ends ■ With end splices
Cable outlet 1/2 NPT conduit	■ With end splices ■ Tinned wire ends
Cable outlet IP68	■ With end splices ■ Tinned wire ends
Cable outlet IP68, FEP	■ With end splices ■ Tinned wire ends
Cable outlet IP6K9K	■ With end splices ■ Tinned wire ends
Short-circuit resistance	S+ vs. U- → Not for ratiometric output signals
Reverse polarity protection	U+ vs. U- → Not for ratiometric output signals
Insulation voltage	DC 750V

Angular connector DIN 175301-803 A

	2-wire	3-wire
U+	1	1
U-	2	2
S+	-	3
Shield (option)	4	4

Angular connector DIN 175301-803 C

	2-wire	3-wire
U +	1	1
U -	2	2
S +	-	3
Shield (option)	4	4

Mating connector with moulded cable

	2-wire	3-wire
U+	Brown (BN)	Brown (BN)
U-	Blue (BU)	Blue (BU)
S+	-	Black (BK)

حساس ضغط

الوصف

المزايا

الأسئلة والأجوبة

اجمع S-20 لمهمتك

أكمل التهيئة

6 مادة قياسية من عائلة S-20