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(МГИ-1М), DPGFT-3 (МГИ-3), DPGU-1 (МСУ-1) and others.
2. Piston downhole pressure gages. The sealed piston is the

sensitive element in the downhole pressure gages of this type. The
measuring pressure is taken up by the sealed piston which is linked

with helical cylindrical spring. The downhole pressure gages of this
type are with immovable and rotary pistons. Downhole pressure gages
of piston type include the following devices: DPGNS-1 (МГН-1),

SSPDPG-4 (МПМ-4), PDPG-3 (МГП-3), PDPG-4 (МГП-4), PDPG-6
(МГП-6), PDPGF (МГПР) and others. They are characterized by
bigger accuracy in comparison with helix downhole pressure gages.

3. Pneumatic downhole pressure gages (downhole differential
pressure gages). The principle of operation of pressure gages of
this type consists in counterbalancing the measuring pressure by the
pressure of gas in the device’s measuring chamber. The downhole

devices of this type record only the increase of the pressure from its
initial magnitude compensated by the pressure of pressed gas.
The downhole devices of this type are called as downhole

differential pressure gages or compensation downhole pressure gages
(compensation downhole differential pressure gages). Downhole
differential pressure gages of this type are the following: DDPG-4M

(ДГМ-4М), DDPG-5 (ДГМ-5), “Samotlor-1”, “Baikal-1” and ”Оnega-

1”.
Helix downhole pressure gages and piston downhole pressure
gages (with the rotary piston) may be with local recording or with
the remote control. Downhole pressure gages with local recording of
both types were used and have still been used in oil and gas fields in
Ukraine and abroad. Helix downhole devices are reliable in operation

and can be used at high temperatures on the bottom hole (up to
о
+ 400 С). Piston downhole pressure gages have a large pressure
recording scale. Piston downhole pressure gages with the rotary piston
are characterized by high accuracy.

11.2.2 The structure and the principle of operation of
the helix downhole pressure gage. Short characteristics of
helix downhole pressure gages

The main advantages of helix downhole pressure gages are their
high reliability at operation process, simplicity of the structure and

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