压力校准高度差修正：基准、符号与密度

Start with the measurand and reference planes

Two 仪表 connected to one static fluid system can experience different 压力s at different elevations. Beamex's 压力-表压 校准 guidance identifies height difference as a source of hydrostatic error, particularly with liquids.

Call the measurement reference R and the device under test D. Use their manufacturer-defined 压力-reference planes. Let z increase upwards and define delta_z = z_D - z_R. This definition must accompany a correction; a height magnitude alone does not specify its sign.

A static model with explicit limits

For a single connected fluid of effectively constant density at rest, the 绝压-压力 relation is p_D_abs = p_R_abs - rho_fluid × g × delta_z. Here density is in kg/m³, g in m/s², height in m and 压力 in Pa.

For two 表压-压力 measurements locally referenced to the same surrounding atmosphere, with effectively constant fluid and air densities over the height difference, the corresponding relation is p_D_表压 = p_R_表压 - (rho_fluid - rho_air) × g × delta_z. Appendix A2.2 of the BIPM-hosted EURAMET.M.P-S14 report provides a 表压-压力 head-correction model including fluid minus air density. Its height convention is opposite to delta_z as defined here.

These are static teaching models, not a universal 校准 procedure. 差压-压力仪表, mixed fluid columns, 压力-dependent density and different reference arrangements need their own documented treatment. A gas head is not automatically negligible for every uncertainty target.

Worked example: D is above R

Assume 表压 压力 at R = 100 kPa, rho_fluid = 1000 kg/m³, rho_air = 1.2 kg/m³, g = 9.80665 m/s² and delta_z = +0.30 m. These are hypothetical inputs, not measured fluid properties or WESIVO specifications.

• The positive head magnitude is (1000 - 1.2) × 9.80665 × 0.30 = 2938.464606 Pa, approximately 2.938 kPa.
• With D above R, 压力 at D is approximately 97.062 kPa 表压.
• With D instead 0.30 m below R, delta_z is negative and 压力 at D is approximately 102.938 kPa 表压.
• At equal reference-plane elevations, this idealised height term is zero; other errors and uncertainties remain.

The corrected reference value at D is the comparison input. It is not the DUT indication error by itself. Determine that error by comparing the DUT indication with the appropriately corrected reference value, following the chosen procedure and sign convention.

Keep the correction auditable

Record both reference-plane identities, signed height and units, fluid and density basis, applicable conditions, 压力 type, equation convention, correction and the uncertainty treatment. EURAMET cg-17 v4.1 includes consideration of uncertainty associated with estimated head correction. Do not replace a documented geometry correction with an unexplained zero adjustment.

Use the density appropriate to the fluid and measurement conditions; the assumed value above is not a universal water or oil density. Have the responsible metrologist decide which effects are significant for the actual range and target uncertainty.

Equipment 选型 is a separate decision

The WESIVO 880 product page and original datasheet support a configuration enquiry. Confirm the ordered 压力 type and range, reference 液位, applicable certificate and intended role. No automatic head-correction capability is asserted here.

The related 522U pump is a 压力-source listing, not a recommendation for this 100 kPa teaching example. Neither the calculation nor these product links establish a validated equipment combination. Send the actual setup drawing and measurement requirements when requesting a quotation.