ANSI SP3.4:2016 pdf free download – Periodic Verification of Air Ionizer Performance Using a Small Test Fixture
5.0 TEST FIXTURE AND INSTRUMENTATION
The following sections describe an example of a test fixture and instrumentation used for periodic verification of air ionization performance in confined spaces. The test fixture in this example uses an isolated conductive plate for air ion collection. The instrumentation may consist of separate components (high voltage [HV] charging source, voltage monitor, voltage threshold detector and timer), or these components may be integrated into a single instrument. The example is not meant to limit the possibilities of the test fixture and instrumentation design in any way. Whatever design is used, the resulting instrumentation should be correlated to those made with a Charged Plate Monitor (CPM) and procedures as described in ANSI/ESD STM3.1 . Refer to Annex B for procedures used to develop the correlation factors between the CPM and the smaller test fixture. The example test fixture consists of an isolated conductive plate separated from a ground plate on insulative standoff(s). Additional instrumentation is used to charge the isolated conductive plate and monitor the voltage (see Figure 1 ). In this example, the isolated conductive plate is 2.54 cm x 2.54 cm (1 inch x 1 inch) with an approximate capacitance of 3 pF when mounted in the test fixture without electrical hookups (see Figure 2). A voltage source that provides a voltage in excess of the initial test voltage of each polarity is required to charge the isolated conductive plate of the test fixture. The voltage source should be current limited so as to meet the requirements of Section 4.0 Personnel Safety. The voltage on the isolated conductive plate shall be monitored in such a way that, when in the absence of ionization, the isolated conductive plate voltage shall not decay more than 1 0% of the initial test voltage within one minute. The response time of the monitoring device shall be sufficient to accurately measure changing voltages. A timer or other appropriate means should be used to measure the discharge times.
6.0 GENERAL MEASUREMENT PROCEDURE
Each ionization application or installation may require a different measurement procedure. Initial and final test voltages should be documented and may be changed if required. The actual measurement procedures and parameters (i.e., equipment, test voltages, test fixture distance and location, air velocity, fan speed settings, compressed gas pressure) should be documented and attached to the test data for use during subsequent periodic verifications. Procedures should be a part of the initial acceptance process to provide baseline data for comparison with future measurements. A schedule should be established for performing periodic verification. The following test steps are common elements to the periodic verification of all types of ionizers for measurements made in confined spaces.