Pressure switches
Mechanical pressure switches
FEMA negative pressure switches detect the
pressure difference relative to atmospheric pressure. All data relating to the setting range and
thus also the scale divisions on the switching
devices are to be understood as the difference
in pressure between the relevant atmospheric
pressure and the set switching pressure.
The “zero” reference point on the scale of the
unit corresponds to the relevant atmospheric
pressure. A minus sign before the pressure value
signifies negative pressure below the relevant
atmospheric pressure.
Technical data
Pressure connection
External thread G 1/2 (pressure gauge connection) according to DIN 16 288 and internal
thread G 1/4 according to ISO 228 Part 1.
Switching device
Robust housing (200) made of seawaterresistant diecast aluminium GD Al Si 12.
Degree of protection
IP 54, in vertical position.
IP 65, for EEx-d version.
Pressure sensor materials
VNM 111 and Metal bellows: 1.4571
VNM 301: Sensor housing: 1.4104
VCM 095, 101 Metal bellows of Cu Zn
and 301: Sensor housing of CuZn
VCM 4156: Perbunan diaphragm sen-
sor housing: 1.4301
Mounting position
Vertically upright and horizontal.
VCM 4156 vertically upright.
Ambient temp. at switching device
–25…+70 °C
For EEx-d versions: –15…+60 °C
Max. medium temperature
The maximum medium temperature at the
pressure sensor must not exceed the permitted
ambient temperature at the switching device.
Temperatures may reach 85°C for short periods (not EEx-d). Higher medium temperatures
are possible provided the above limit values for
the switching device are ensured by suitable
measures (e.g. siphon).
Mounting
Directly on the pressure line (pressure gaugeconnection) or on a flat surface with two
4 mm Ø screws.
Switching pressure
Adjustable from outside with screwdriver.
Switching differential
Not adjustable with VCM and Ex-VCM types.
Adjustable with VCM-203 type.
For values see Product Summary.
Contact arrangement
Single-pole changeover switch.
Switching
capacity
VCM type series
Negative pressure switches (vacuum switches)
VCM 301
VNM 111
Type Setting range Switching Max. Dimen-
differential permissible sioned
(mean values) pressure drawing
Switching differential not adjustable
VCM 4156 -15…+6 mbar 2 mbar 1 bar 1 + 11
VCM 301 -250…+100 mbar 25 mbar 1.5 bar 1 + 13
VNM 301 –250…+100 mbar 45 mbar 3 bar 1 + 15
VCM 101 –1*…+0.1 bar 45 mbar 3 bar 1 + 14
VCM 095 –0.9…+0.5 bar 50 mbar 3 bar 1 + 14
VNM 111 –1*…+0.1 bar 50 mbar 6 bar 1 + 15
Switching differential adjustable
VCM 301-203 –250…+100 mbar 30–200 mbar 1.5 bar 1 + 13
VNM 301-203 –250…+100 mbar 70 –500 mbar 3 bar 1 + 15
VCM 101-203 –1*…+0.1 bar 80 –350 mbar 3 bar 1 + 14
VCM 095-203 –0.9….+0.5 bar 90 –400 mbar 3 bar 1 + 14
VNM 111-203 –1*…+0.1 bar 90 –650 mbar 6 bar 1 + 15
version, (housing 700), explosion protection EEx-d
Ex-VCM 4156 –15…+6 mbar 2 mbar 1 bar 3 + 11
Ex-VCM 301 –250…+100 mbar 25 mbar 1.5 bar 3 + 13
Ex-VNM 301 –250…+100 mbar 45 mbar 3 bar 3 + 15
Ex-VCM 101 –1*…+0.1 bar 45 mbar 3 bar 3 + 14
Ex-VCM 095 –0.9…+0.5 bar 50 mbar 3 bar 3 + 14
Ex-VNM 111 –1*…+0.1 bar 50 mbar 6 bar 3 + 15
Product Summary
Degree of protection:
IP 54/65
s
* At very high vacuums, close to the theoretical maximum of –1 bar, the switch may not be usable in
view of the special conditions of vacuum engineering. However, the pressure switch itself will not be
damaged at maximum vacuum.
For additional functions refer to ZF data sheet.
For smaller pressure ranges see also HCD and DPS data sheets.
Calibration
The VCM and VNM series are calibrated for falling pressure. This means that the adjustable switching
pressure on the scale corresponds to the switching point at falling pressure. The reset point is higher
by the amount of the switching differential. (See also page 30, 1. Calibration at lower switching point).
250 VAC 250 VDC 24 VDC
(ohm) (ind) (ohm) (ohm)
Normal 8 A 5 A 0.3 A 8 A
EEx-d 3 A 2 A 0.03 A 3 A
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