Describe both sides of the measurement
Identify the high and low connections, the medium at each port and the direction in which differential pressure is normally applied. State if the readings can cross zero. A low differential across a pressurised line and a low differential between rooms can call for different handling arrangements.
Name the instrument and reporting point
For a handheld manometer, include its resolution and any adaptors that normally travel with it. For a transmitter, describe the display or electrical output used by the operator. If your process has an alarm threshold, supply that value and ask for the scope of the alarm check separately.
Choose points around the operating decision
A room monitor can spend most of its time close to an alarm limit, while a filter monitor may use a much wider part of its span. Include the normal reading and relevant limit with the requested calibration points. Where the displayed difference can be positive or negative, list both signs explicitly so a purchase order cannot be read as a one-direction request.
State whether the low port will be open to atmosphere or whether both sides operate under pressure. The pressure common to both ports is a separate condition from their difference. Include that condition for review rather than assuming a bench check reproduces the installation. If the request includes an analogue output, give its scaling and identify the reading used for acceptance. Zero adjustment, display comparison and an alarm check should be identifiable on the agreed scope.
Coordinate work across adjacent rooms
Identify the monitor available for removal and the person controlling access to its location. Keep the room designation and equipment tag beside each entry when several identical meters share an order. Include any tubing or adapters that need to stay paired with the unit, following the site's removal procedure.